CBQE-0: Add timeout default value in _verify_all_buckets

Change-Id: I21dc05ee51e9faf929da79094b0badcd428f8bf6
Reviewed-on: http://review.couchbase.org/30788
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>