shutdown niql service carefully by sending it shutdown message
shutdown niql service carefully by sending it shutdown message

Change-Id: I7f99a0296850b241e7939514ad43dc37f600a3b9
Reviewed-on: http://review.couchbase.org/43154
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

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