[SCSI] scsi_error regression: Fix idempotent command handling

Drivers want to be able to return DID_TRANSPORT_DISRUPTED and
have it do the right thing for commands like tape and passthrouh
as far as retries go. The LLDs previously used DID_BUS_BUSY or DID_ERROR
which followed the cmd->retries limit, but DID_TRANSPORT_DISRUPTED
was skipping that check so it could have caused a problem with tape
commands.

This patch has DID_TRANSPORT_DISRUPTED check the cmd->retries/cmd->allowed.
Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/scsi_error.c

@@ -1340,9 +1340,10 @@ int scsi_decide_disposition(struct scsi_cmnd *scmd)
 		 * LLD/transport was disrupted during processing of the IO.
 		 * The transport class is now blocked/blocking,
 		 * and the transport will decide what to do with the IO
-		 * based on its timers and recovery capablilities.
+		 * based on its timers and recovery capablilities if
+		 * there are enough retries.
 		 */
-		return ADD_TO_MLQUEUE;
+		goto maybe_retry;
 	case DID_TRANSPORT_FAILFAST:
 		/*
 		 * The transport decided to failfast the IO (most likely