[test suite] minor comment addition so this isn't a zero-byte file
[test suite] add new test files to Makefile.am
[server] minor memory leak bug fix for invalid date processing

Bug fix to ensure to release memory when invalid access stanza dates are set
and fwknopd has to exit.  This leak was caught with the test suite in
--enable-valgrind mode based on the following output:

==31947== 568 bytes in 1 blocks are still reachable in loss record 1 of 1
==31947==    at 0x4C2CD7B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==31947==    by 0x52EE42A: __fopen_internal (iofopen.c:73)
==31947==    by 0x1116A2: parse_access_file (access.c:909)
==31947==    by 0x10BAD5: main (fwknopd.c:194)
[server] added tests on Linux systems for the iptables FLUSH_IPT_* vars