[SCSI] fix oops on usb storage device disconnect

We fix the oops by enforcing the host state model.  There have also
been two extra states added: SHOST_CANCEL_RECOVERY and
SHOST_DEL_RECOVERY so we can take the model through host removal while
the recovery thread is active.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index f065cbc..dc9c772 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -447,7 +447,7 @@
 
 	spin_lock_irqsave(shost->host_lock, flags);
 	shost->host_busy--;
-	if (unlikely((shost->shost_state == SHOST_RECOVERY) &&
+	if (unlikely(scsi_host_in_recovery(shost) &&
 		     shost->host_failed))
 		scsi_eh_wakeup(shost);
 	spin_unlock(shost->host_lock);
@@ -1339,7 +1339,7 @@
 				   struct Scsi_Host *shost,
 				   struct scsi_device *sdev)
 {
-	if (shost->shost_state == SHOST_RECOVERY)
+	if (scsi_host_in_recovery(shost))
 		return 0;
 	if (shost->host_busy == 0 && shost->host_blocked) {
 		/*