batman-adv: Fix consistency of update route messages

The debug messages of _batadv_update_route were printed before the actual
route change is done. At this point it is not really known which
curr_router will be replaced. Thus the messages could print the wrong
operation.

Printing the debug messages after the operation was done avoids this
problem.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>