engine: Propagate error message when quering for LDAP users/groups

Propagating error message when searching AD users/groups via SearchQuery fails,
The error is propagated to the webadmin and an inline error message is displayed within the
permission view popup.

Change-Id: I50da72d12c6d60642ad5e65b9376efc49e4ef699
Signed-off-by: Asaf Shakarchi <asaf@redhat.com>