MB-8013 Notify rebalance start/end for memcached buckets too.
MB-8013 Notify rebalance start/end for memcached buckets too.

Change-Id: Iaad86e209a9b49ce663ffdc9b10f90d77cfddd95
Reviewed-on: http://review.couchbase.org/25907
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

ceejatec/ns_server,vzasade/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,vzasade/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,mschoch/ns_server,ceejatec/ns_server,nimishzynga/ns_server,mschoch/ns_server,pavel-blagodov/ns_server,nimishzynga/ns_server,mschoch/ns_server,vzasade/ns_server,t3rm1n4l/ns_server,vzasade/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,nimishzynga/ns_server,mschoch/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,daverigby/ns_server,daverigby/ns_server,nimishzynga/ns_server,mschoch/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,mschoch/ns_server,membase/ns_server,pavel-blagodov/ns_server