nvme-fabrics: avoid double completions in nvmf_fail_nonready_command

When reconnecting, the request may be completed with
NVME_SC_HOST_PATH_ERROR in nvmf_fail_nonready_command, which currently
set the state of the request to MQ_RQ_IN_FLIGHT before calling
nvme_complete_rq.  When this happens for a request that is freed by
the caller, such as nvme_submit_user_cmd, in the worst case the request
could be completed again in tear down process.

Instead of calling blk_mq_start_request from nvmf_fail_nonready_command,
just use the new nvme_host_path_error helper to complete the command
without starting it.

Signed-off-by: Chao Leng <lengchao@huawei.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>