The pki debug log has its name in this format: debug.<date>.log. This commit
changes the code to use this format, fixing the test.
Unfortunately, it's not possible to use some kind of regex (like debug.*.log)
to get the file, because python multihost gets the path and tries to open
(using the "open" python function) the file with that.
https://pagure.io/freeipa/issue/7095
Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>