[SCSI] libiscsi, iscsi_tcp, ib_iser: fix setting of can_queue with old tools.

This patch fixes two bugs that are related.

1. Old tools did not set can_queue/cmds_max. This patch modifies
libiscsi so that when we add the host we catch this and set it
to the default.

2. iscsi_tcp thought that the scsi command that was passed to
the eh functions needed a iscsi_cmd_task allocated for it. It
only needed a mgmt task, and now it does not matter since it
all comes from the same pool and libiscsi handles this for the
drivers. ib_iser had copied iscsi_tcp's code and set can_queue
to its max - 1 to handle this. So this patch removes the max -1,
and just sets it to the max.
Signed-off-by: NMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

drivers/infiniband/ulp/iser/iscsi_iser.c

@@ -595,7 +595,6 @@ static struct scsi_host_template iscsi_iser_sht = {
 	.name                   = "iSCSI Initiator over iSER, v." DRV_VER,
 	.queuecommand           = iscsi_queuecommand,
 	.change_queue_depth	= iscsi_change_queue_depth,
-	.can_queue		= ISCSI_DEF_XMIT_CMDS_MAX - 1,
 	.sg_tablesize           = ISCSI_ISER_SG_TABLESIZE,
 	.max_sectors		= 1024,
 	.cmd_per_lun            = ISCSI_MAX_CMD_PER_LUN,

drivers/scsi/iscsi_tcp.c

@@ -1865,7 +1865,6 @@ iscsi_tcp_session_create(struct iscsi_endpoint *ep, uint16_t cmds_max,
 	shost->max_id = 0;
 	shost->max_channel = 0;
 	shost->max_cmd_len = SCSI_MAX_VARLEN_CDB_SIZE;
-	shost->can_queue = cmds_max;
 
 	if (iscsi_host_add(shost, NULL))
 		goto free_host;

drivers/scsi/libiscsi.c

@@ -1857,6 +1857,9 @@ EXPORT_SYMBOL_GPL(iscsi_pool_free);
  */
 int iscsi_host_add(struct Scsi_Host *shost, struct device *pdev)
 {
+	if (!shost->can_queue)
+		shost->can_queue = ISCSI_DEF_XMIT_CMDS_MAX;
+
 	return scsi_add_host(shost, pdev);
 }
 EXPORT_SYMBOL_GPL(iscsi_host_add);
@@ -1942,6 +1945,9 @@ iscsi_session_setup(struct iscsi_transport *iscsit, struct Scsi_Host *shost,
 	struct iscsi_session *session;
 	struct iscsi_cls_session *cls_session;
 	int cmd_i, scsi_cmds, total_cmds = cmds_max;
+
+	if (!total_cmds)
+		total_cmds = ISCSI_DEF_XMIT_CMDS_MAX;
 	/*
 	 * The iscsi layer needs some tasks for nop handling and tmfs,
 	 * so the cmds_max must at least be greater than ISCSI_MGMT_CMDS_MAX