* get_usr_preference now always returns a ResultSet object as it
expected. If there is no preference found an empty ResultSet
object is returned that does not have ->first. That is
now in line with how the usage of the function works in the current
codebase and should not produce errors when there was a preference
requested that did not exist and 'undef' was returned instead of
an object.
* remove 'skipping' debug code that caused a lot of spam in the
panel-debug.log reporting skipped usr preferences for
'subscriberadmin' and 'subscriber' roles
Change-Id: Ia9d033994e36afd48c2b6d91b08163f871a71b4c