batman-adv: increase BLA wait periods to 6

If networks take a long time to come up, e.g. due to lossy links, then
the bridge loop avoidance wait time to suppress broadcasts may not wait
long enough and detect a backbone before the mesh is brought up.
Increasing the wait period further to 60 seconds makes this scenario
less likely.

Signed-off-by: Simon Wunderlich <simon@open-mesh.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>