tests: Introduce check-file-access.pl

tests: Introduce check-file-access.pl

This script will check output generated by virtestmock against a
white list. All non matching records found are printed out. So
far, the white list is rather sparse at the moment.
This test should be ran only after all other tests finished, and
should cleanup the temporary file before their execution. Because
I'm unable to reflect these requirements in Makefile.am
correctly, I've introduced new target 'check-access' under which
this test is available.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>