CBQE-0: fix failover failures and async load buckets

Change-Id: Ied3cfad450712df70af58f66acbffbd8384f554a
Reviewed-on: http://review.couchbase.org/36538
Reviewed-by: Ketaki Gangal <ketakigangal@gmail.com>
Reviewed-by: Parag Agarwal <agarwal.parag@gmail.com>
Tested-by: Parag Agarwal <agarwal.parag@gmail.com>