Fix the issue with schedule backup of internal DB 

that failed due to calling LogFile.verify_log_depot_settings that has been removed in https://github.com/ManageIQ/manageiq/pull/908.

https://bugzilla.redhat.com/show_bug.cgi?id=1173213
This seems backwards to me.  You are looking up a key by a value.  Why not flip it and look up the value by key likea normal Hash operation?