make sure that ns_process_registry does not attempt to kill itself

... on terminate

Change-Id: I04a451ad78870daef55f26f448761a7227b84c5e
Reviewed-on: http://review.couchbase.org/38710
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>