aaa: Associate users only with managed groups by oVirt

This patch will store at groupNames only groups that are managed
by Ovirt (i.e - groups that exist in the groups DB table).

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1120720
Change-Id: I8a5daf3c68cc04ebd4ad0ec6cfdfd6cf16ececb9
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>