wakeup streaming connections on membership change

So that /pools/default/bs/<bucket> gets updated on failover of
non-data node.

Change-Id: Ib6dcd5ab5e3a130350531314f12c3ed1ea4e72fe
Reviewed-on: http://review.couchbase.org/44630
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>