aaa: more fixes to sync and usages

More fixes were introcued to sync and usages- especially around
adding an already added group/principal.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1120720
Change-Id: I0d6198409b7c3e66054716e1abdfcd06e8dd204d
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>