nvme-tcp: break from io_work loop if recv failed

If we failed to receive data from the socket, don't try
to further process it, we will for sure be handling a queue
error at this point. While no issue was seen with the
current behavior thus far, its safer to cease socket processing
if we detected an error.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>