nvme-rdma: only clear queue flags after successful connect

Otherwise, nvme_rdma_stop_and_clear_queue() will incorrectly
try to stop/free rdma qps/cm_ids that are already freed.

Fixes: e89ca58f ("nvme-rdma: add DELETING queue flag")
Reported-by: Steve Wise <swise@opengridcomputing.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>