bp:leave cluster once when we detect that we were ejected.MB-4310
bp:leave cluster once when we detect that we were ejected.MB-4310

Change-Id: I3cac959b3087f83227453ad6001ae5894bf9f799
Orig-Reviewed-on: http://review.couchbase.org/9887
Reviewed-on: http://review.couchbase.org/13274
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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