CCBC-385: Handle CMD_GET_REPLICA in failout_single_request

Change-Id: Ib3833eafa99ba88c027c15cd3554fc583f07e9ae
Reviewed-on: http://review.couchbase.org/36139
Reviewed-by: Yury Alioshinov <haster2010@gmail.com>
Tested-by: Yury Alioshinov <haster2010@gmail.com>
Reviewed-by: Brett Lawson <brett19@gmail.com>