Fix uninitialized path variable

This function needs to be revisited to solve the 4k problem, however
there is a much more critical bug here, where path is uninitialized
before use.

imo this ought to be merged soon, and then we can worry about 4k-sanitizing this function, since that will presumably take a lot longer.

My test case for the valgrind output below was running valgrind on cf-agent running through the entirety of LinkedIn's policy set.

Valgrind output before (also includes a different bug that I fixed):
```
==29838== Memcheck, a memory error detector
==29838== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
==29838== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
==29838== Command: /var/cfengine/bin/cf-agent -KI
==29838== Parent PID: 29836
==29838== 
==29838== Conditional jump or move depends on uninitialised value(s)
==29838==    at 0x3E6D2480AC: vfprintf (in /lib64/libc-2.12.so)
==29838==    by 0x3E6D26F659: vasprintf (in /lib64/libc-2.12.so)
==29838==    by 0x4C93205: xvasprintf (alloc.c:83)
==29838==    by 0x4C953C6: StringVFormat (string_lib.c:40)
==29838==    by 0x4C99164: VLog (logging.c:239)
==29838==    by 0x4C992C7: Log (logging.c:305)
==29838==    by 0x4376CE: SelectLeaf (files_select.c:189)
==29838==    by 0x414891: DepthSearch (verify_files_utils.c:2235)
==29838==    by 0x40FB78: VerifyFilePromise (verify_files.c:413)
==29838==    by 0x444790: LocateFilePromiserGroup (promiser_regex_resolver.c:61)
==29838==    by 0x410508: FindAndVerifyFilesPromises (verify_files.c:793)
==29838==    by 0x40B923: KeepAgentPromise (cf-agent.c:1735)
==29838== 
==29838== Invalid write of size 1
==29838==    at 0x429D20: MakeTemporaryBundleFromTemplate (files_editline.c:267)
==29838==    by 0x40E9EE: ScheduleEditOperation (verify_files.c:512)
==29838==    by 0x40FC6F: VerifyFilePromise (verify_files.c:461)
==29838==    by 0x444790: LocateFilePromiserGroup (promiser_regex_resolver.c:61)
==29838==    by 0x410508: FindAndVerifyFilesPromises (verify_files.c:793)
==29838==    by 0x40B923: KeepAgentPromise (cf-agent.c:1735)
==29838==    by 0x4C6EE64: ExpandPromise (expand.c:202)
==29838==    by 0x40B0EF: ScheduleAgentOperations (cf-agent.c:1243)
==29838==    by 0x40D4E7: main (cf-agent.c:1158)
==29838==  Address 0x74ed0bf is 1 bytes before a block of size 1 alloc'd
==29838==    at 0x4A0577B: calloc (vg_replace_malloc.c:593)
==29838==    by 0x4C933A8: xcalloc (alloc.c:47)
==29838==    by 0x429CB9: MakeTemporaryBundleFromTemplate (files_editline.c:258)
==29838==    by 0x40E9EE: ScheduleEditOperation (verify_files.c:512)
==29838==    by 0x40FC6F: VerifyFilePromise (verify_files.c:461)
==29838==    by 0x444790: LocateFilePromiserGroup (promiser_regex_resolver.c:61)
==29838==    by 0x410508: FindAndVerifyFilesPromises (verify_files.c:793)
==29838==    by 0x40B923: KeepAgentPromise (cf-agent.c:1735)
==29838==    by 0x4C6EE64: ExpandPromise (expand.c:202)
==29838==    by 0x40B0EF: ScheduleAgentOperations (cf-agent.c:1243)
==29838==    by 0x40D4E7: main (cf-agent.c:1158)
==29838== 
==29838== Conditional jump or move depends on uninitialised value(s)
==29838==    at 0x4A07F59: strlen (mc_replace_strmem.c:403)
==29838==    by 0x4C715C8: LastFileSeparator (files_names.c:385)
==29838==    by 0x4C71608: ReadLastNode (files_names.c:535)
==29838==    by 0x437154: SelectLeaf (files_select.c:399)
==29838==    by 0x414891: DepthSearch (verify_files_utils.c:2235)
==29838==    by 0x40FB78: VerifyFilePromise (verify_files.c:413)
==29838==    by 0x444790: LocateFilePromiserGroup (promiser_regex_resolver.c:61)
==29838==    by 0x410508: FindAndVerifyFilesPromises (verify_files.c:793)
==29838==    by 0x40B923: KeepAgentPromise (cf-agent.c:1735)
==29838==    by 0x4C6EE64: ExpandPromise (expand.c:202)
==29838==    by 0x40B0EF: ScheduleAgentOperations (cf-agent.c:1243)
==29838==    by 0x40D4E7: main (cf-agent.c:1158)
==29838== 
==29838== Conditional jump or move depends on uninitialised value(s)
==29838==    at 0x4A0849C: strcmp (mc_replace_strmem.c:729)
==29838==    by 0x40E6A6: FullTextMatch (match_scope.c:91)
==29838==    by 0x437164: SelectLeaf (files_select.c:399)
==29838==    by 0x414891: DepthSearch (verify_files_utils.c:2235)
==29838==    by 0x40FB78: VerifyFilePromise (verify_files.c:413)
==29838==    by 0x444790: LocateFilePromiserGroup (promiser_regex_resolver.c:61)
==29838==    by 0x410508: FindAndVerifyFilesPromises (verify_files.c:793)
==29838==    by 0x40B923: KeepAgentPromise (cf-agent.c:1735)
==29838==    by 0x4C6EE64: ExpandPromise (expand.c:202)
==29838==    by 0x40B0EF: ScheduleAgentOperations (cf-agent.c:1243)
==29838==    by 0x40D4E7: main (cf-agent.c:1158)
==29838== 
==29838== Conditional jump or move depends on uninitialised value(s)
==29838==    at 0x4A084C7: strcmp (mc_replace_strmem.c:729)
==29838==    by 0x40E6A6: FullTextMatch (match_scope.c:91)
==29838==    by 0x437164: SelectLeaf (files_select.c:399)
==29838==    by 0x414891: DepthSearch (verify_files_utils.c:2235)
==29838==    by 0x40FB78: VerifyFilePromise (verify_files.c:413)
==29838==    by 0x444790: LocateFilePromiserGroup (promiser_regex_resolver.c:61)
==29838==    by 0x410508: FindAndVerifyFilesPromises (verify_files.c:793)
==29838==    by 0x40B923: KeepAgentPromise (cf-agent.c:1735)
==29838==    by 0x4C6EE64: ExpandPromise (expand.c:202)
==29838==    by 0x40B0EF: ScheduleAgentOperations (cf-agent.c:1243)
==29838==    by 0x40D4E7: main (cf-agent.c:1158)
==29838== 
==29838== Conditional jump or move depends on uninitialised value(s)
==29838==    at 0x40E6B0: FullTextMatch (match_scope.c:91)
==29838==    by 0x437164: SelectLeaf (files_select.c:399)
==29838==    by 0x414891: DepthSearch (verify_files_utils.c:2235)
==29838==    by 0x40FB78: VerifyFilePromise (verify_files.c:413)
==29838==    by 0x444790: LocateFilePromiserGroup (promiser_regex_resolver.c:61)
==29838==    by 0x410508: FindAndVerifyFilesPromises (verify_files.c:793)
==29838==    by 0x40B923: KeepAgentPromise (cf-agent.c:1735)
==29838==    by 0x4C6EE64: ExpandPromise (expand.c:202)
==29838==    by 0x40B0EF: ScheduleAgentOperations (cf-agent.c:1243)
==29838==    by 0x40D4E7: main (cf-agent.c:1158)
==29838== 
==29838== Conditional jump or move depends on uninitialised value(s)
==29838==    at 0x4A07F59: strlen (mc_replace_strmem.c:403)
==29838==    by 0x40E4D9: RegExMatchSubString (match_scope.c:39)
==29838==    by 0x40E6F4: FullTextMatch (match_scope.c:77)
==29838==    by 0x437164: SelectLeaf (files_select.c:399)
==29838==    by 0x414891: DepthSearch (verify_files_utils.c:2235)
==29838==    by 0x40FB78: VerifyFilePromise (verify_files.c:413)
==29838==    by 0x444790: LocateFilePromiserGroup (promiser_regex_resolver.c:61)
==29838==    by 0x410508: FindAndVerifyFilesPromises (verify_files.c:793)
==29838==    by 0x40B923: KeepAgentPromise (cf-agent.c:1735)
==29838==    by 0x4C6EE64: ExpandPromise (expand.c:202)
==29838==    by 0x40B0EF: ScheduleAgentOperations (cf-agent.c:1243)
==29838==    by 0x40D4E7: main (cf-agent.c:1158)
==29838== 
==29838== 
==29838== HEAP SUMMARY:
==29838==     in use at exit: 861,201 bytes in 6,882 blocks
==29838==   total heap usage: 148,127,673 allocs, 148,120,791 frees, 10,776,399,795 bytes allocated
==29838== 
==29838== LEAK SUMMARY:
==29838==    definitely lost: 192,576 bytes in 2,230 blocks
==29838==    indirectly lost: 509,454 bytes in 2,197 blocks
==29838==      possibly lost: 0 bytes in 0 blocks
==29838==    still reachable: 159,171 bytes in 2,455 blocks
==29838==         suppressed: 0 bytes in 0 blocks
==29838== Rerun with --leak-check=full to see details of leaked memory
==29838== 
==29838== For counts of detected and suppressed errors, rerun with: -v
==29838== Use --track-origins=yes to see where uninitialised values come from
==29838== ERROR SUMMARY: 29 errors from 7 contexts (suppressed: 6 from 6)
```

and after:

```
==20417== Memcheck, a memory error detector
==20417== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
==20417== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
==20417== Command: /var/cfengine/bin/cf-agent -KI
==20417== Parent PID: 20415
==20417== 
==20417== 
==20417== HEAP SUMMARY:
==20417==     in use at exit: 861,360 bytes in 6,888 blocks
==20417==   total heap usage: 148,192,330 allocs, 148,185,442 frees, 10,786,793,854 bytes allocated
==20417== 
==20417== LEAK SUMMARY:
==20417==    definitely lost: 192,576 bytes in 2,230 blocks
==20417==    indirectly lost: 508,697 bytes in 2,196 blocks
==20417==      possibly lost: 907 bytes in 5 blocks
==20417==    still reachable: 159,180 bytes in 2,457 blocks
==20417==         suppressed: 0 bytes in 0 blocks
==20417== Rerun with --leak-check=full to see details of leaked memory
==20417== 
==20417== For counts of detected and suppressed errors, rerun with: -v
==20417== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from 6)
```
Reading into uninitialized wouldn't necessarily cause a crash, unless we overflowed into memory that we weren't allowed to write into or used the value as an address to dereference. Neither of those things were the case here, instead it just passed a garbage path name.