profiles: ad: move to upn based principals

using samAccountName have lots of performance advantages, however, there
is limitation on the length of user name, which is truncated past N
characters.

so we move to upn based principals, which requires accessing gc. the
implementation is simpler than the sam based.

from now the gc access is mandatory.

Change-Id: Ic7d4d15b19a6fc3506fdaaaa9a1f0c95eefdc572
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>