batman-adv: Don't handle address updates when bla is disabled

The bridge loop avoidance has a hook to handle address updates of the
originator. These should not be handled when bridge loop avoidance is
disabled - it might send some bridge loop avoidance packets which should
not appear if bla is disabled.

Signed-off-by: Simon Wunderlich <simon@open-mesh.com>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>