Fix a printf for new code

We now also check ATTR_DEVICE.

Signed-off-by: Andy Grover <agrover@redhat.com>
Fix up cmd_submit in main and handler

Change cmd_submit to take the cdb and iovecs, and return handled or
not-handled. Based on this, the runner sets the scsi status and sense
info, if needed.

Remove duplicated code from runner and handler.

Signed-off-by: Andy Grover <agrover@redhat.com>
Save a pointer to handler in tcmu_device

Seems handy.

Signed-off-by: Andy Grover <agrover@redhat.com>