nvme-tcp: fix UAF when detecting digest errors

We should also bail from the io_work loop when we set rd_enabled to true,
so we don't attempt to read data from the socket when the TCP stream is
already out-of-sync or corrupted.

Fixes: 3f2304f8

 ("nvme-tcp: add NVMe over TCP host driver")
Reported-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>