aaa: Adding namespace dropdown list to "add user" dialog

This both adds the namespace dropdown list and fixes
search to support namespace

Topic: AAA
Bug-Url: https://bugzilla.redhat.com/1117502
Change-Id: Ic78559243c765271bf8e12abd035deba05226bda
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>