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
I guess it's not a concern right now since only NFS and SMB are in the list, but eventually we should probably use ```FileDepot.supported_depots``` and the methods on the subclasses.