scsi: set correct completion code in scsi_send_eh_cmnd()

->queuecommand returns '0' for successful command submission,
so we need to set the correct SCSI midlayer return value
when calling scsi_log_completion().

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reported-by: Robert Elliott <elliott@hp.com>
Cc: Stephen Cameron <scameron@beardog.cce.hp.com>
Tested-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>