lock down ns_server in toy-trondn.xml

Change-Id: Ifd7a58ab85cbf5b3dbbbd42f8df4a2367132e28b
Reviewed-on: http://review.couchbase.org/32798
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>