server_negotiate: always release ringbuffer

Otherwise, memory will leak

Change-Id: I5f1ae990c57cd9ed090f482ac44070ffd8036383
Reviewed-on: http://review.couchbase.org/32878
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>