scsi: libiscsi: Fix error count for active session

Fix an error count for active session if the total_cmds is invalid on the
function iscsi_session_setup().  Decrement the number of active sessions
before the funcion return.

Link: https://lore.kernel.org/r/EDBAAA0BBBA2AC4E9C8B6B81DEEE1D6916A28542@DGGEML525-MBS.china.huawei.comReviewed-by: Lee Duncan <lduncan@suuse.com>
Signed-off-by: Wu Bo <wubo40@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/libiscsi.c

@@ -2771,7 +2771,7 @@ iscsi_session_setup(struct iscsi_transport *iscsit, struct Scsi_Host *shost,
 		       "must be a power of 2.\n", total_cmds);
 		total_cmds = rounddown_pow_of_two(total_cmds);
 		if (total_cmds < ISCSI_TOTAL_CMDS_MIN)
-			return NULL;
+			goto dec_session_count;
 		printk(KERN_INFO "iscsi: Rounding can_queue to %d.\n",
 		       total_cmds);
 	}