batman-adv: process broadcast packets in BLA earlier

The logic in the BLA mechanism may decide to drop broadcast packets
because the node may still be in the setup phase. For this reason,
further broadcast processing like the early client detection mechanism
must be done only after the BLA check.

This patches moves the invocation to BLA before any other broadcast
processing.

This was introduced 30cfd02b
("batman-adv: detect not yet announced clients")

Reported-by: Glen Page <glen.page@thet.net>
Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>