aaa: sync: copy isAdmin from existing user

in role based security there should be no duplication of roles, but in
ovirt-engine schema we have isAdmin marker, although the role can be
queried.

temporary solution is to copy existing user's bit into synced user.

long term solution is to remove this duplication.

Topic: AAA
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1120720
Change-Id: Id62a2a774c102e3e31c022456809b4b2eb2319b2
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>