[SCSI] zfcp: prevent double decrement on host_busy while being busy

The zfcp_scsi_queuecommand was not acting according to the standard
when the respective unit was not available. In this case an -EBUSY was
returned, which is not valid in itself, and in addition scsi_done
was called. This combination is not allowed and was leading to a
double finish of the request and therefor double decrement of the
host_busy counter.
Signed-off-by: NSwen Schillig <swen@vnet.ibm.com>
Signed-off-by: NChristof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

drivers/s390/scsi/zfcp_scsi.c

@@ -88,7 +88,7 @@ static int zfcp_scsi_queuecommand(struct scsi_cmnd *scpnt,
 	ret = zfcp_fsf_send_fcp_command_task(adapter, unit, scpnt, 0,
 					     ZFCP_REQ_AUTO_CLEANUP);
 	if (unlikely(ret == -EBUSY))
-		zfcp_scsi_command_fail(scpnt, DID_NO_CONNECT);
+		return SCSI_MLQUEUE_DEVICE_BUSY;
 	else if (unlikely(ret < 0))
 		return SCSI_MLQUEUE_HOST_BUSY;