unfreeze master reference of ns_server

Because make simple-test is passing. Sometimes...

Change-Id: I1bf91dad008fdc816b214003c18b2e481151092f
Reviewed-on: http://review.couchbase.org/32891
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>