refresh bucket info cache on node's membership changes
refresh bucket info cache on node's membership changes

So that we refresh bucket info cache on niql node failover.

Change-Id: I862f2ff95eac7c481f9662f020a85e7fd9919537
Reviewed-on: http://review.couchbase.org/43152
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

mschoch/ns_server,membase/ns_server,mschoch/ns_server,mschoch/ns_server,mschoch/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,nimishzynga/ns_server,mschoch/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,nimishzynga/ns_server,membase/ns_server,ceejatec/ns_server,nimishzynga/ns_server,ceejatec/ns_server,membase/ns_server,nimishzynga/ns_server,ceejatec/ns_server,membase/ns_server,ceejatec/ns_server,nimishzynga/ns_server