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
Also, I feel like this mapping doesn't belong here and should be in a more common location.  protocol => class seems mapping seems basic enough to just live as a constant in file_depot.rb.  @brandondunne Thoughts?