ds_sds_session_select_checklist should return XCCDF source.
Start using XCCDF source from DataStream.

We still dump the XCCDF to a disk among all the files from catalog,
but we no longer parse XCCDF twice in the xccdf_session.
Plug a memory leak.

Addressing:
4,096 bytes in 1 blocks are definitely lost in loss record 4 of 4
   at 0x4A0645D: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x33AD842F4B: realpath@@GLIBC_2.3 (canonicalize.c:78)
   by 0x4C60848: oscap_acquire_guess_realpath (oscap_acquire.c:233)
   by 0x4C66C5E: ds_sds_dump_component (sds.c:226)
   by 0x4C66E9B: ds_sds_dump_component_ref_as (sds.c:263)
   by 0x4C671CD: ds_sds_dump_component_ref_as (sds.c:320)
   by 0x4C66449: ds_sds_session_register_component_with_dependencies (ds_sds_session.c:240)
   by 0x4C66085: ds_sds_session_select_checklist (ds_sds_session.c:174)
   by 0x4CFBBF0: xccdf_session_load_xccdf (xccdf_session.c:408)
   by 0x4CFB8DA: xccdf_session_load (xccdf_session.c:351)
   by 0x40BCB4: app_evaluate_xccdf (oscap-xccdf.c:469)
   by 0x407EA0: oscap_module_call (oscap-tool.c:261)
Plug a memory leak

Addressing:
7 bytes in 1 blocks are definitely lost in loss record 1 of 2
   at 0x4A0645D: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x3D134AE548: xmlStrndup (xmlstring.c:45)
   by 0x4C6ABAC: ds_rds_add_ai_from_xccdf_results (rds.c:311)
   by 0x4C6B9DF: ds_rds_add_xccdf_test_results (rds.c:688)
   by 0x4C6BDC4: ds_rds_create_from_dom (rds.c:760)
   by 0x4C6C08A: ds_rds_create (rds.c:826)
   by 0x4CFE994: xccdf_session_export_arf (xccdf_session.c:1340)
   by 0x40BF41: app_evaluate_xccdf (oscap-xccdf.c:515)
   by 0x407EA0: oscap_module_call (oscap-tool.c:261)
   by 0x40831D: oscap_module_process (oscap-tool.c:346)
   by 0x406CD6: main (oscap.c:79
Avoid using session->xccdf.source
Drop session->xccdf.file property.
Drop XCCDF_XML literal constant
Do not set target_directory for sds_session.

It is no longer needed because we derive path to XCCDF from the
sds_session and not from xccdf_session. (Hence the temp_dir doesn't
need to be shared.