CCBC-472: update ht_nodes when receiving new config

This lets lcb_get_server_list work properly to receive new nodes

Change-Id: I5b4a06c5a83f0f5db5f21e89ec4bd6195cc9d6a4
Reviewed-on: http://review.couchbase.org/39158
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>