iscsi-target: Only perform wait_for_tasks when performing shutdown

This patch changes transport_generic_free_cmd() to only wait_for_tasks
when shutdown=true is passed to iscsit_free_cmd().

With the advent of >= v3.10 iscsi-target code using se_cmd->cmd_kref,
the extra wait_for_tasks with shutdown=false is unnecessary, and may
end up causing an extra context switch when releasing WRITEs.

Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/iscsi/iscsi_target_util.c

@@ -736,7 +736,7 @@ void iscsit_free_cmd(struct iscsi_cmd *cmd, bool shutdown)
 		 * Fallthrough
 		 */
 	case ISCSI_OP_SCSI_TMFUNC:
-		rc = transport_generic_free_cmd(&cmd->se_cmd, 1);
+		rc = transport_generic_free_cmd(&cmd->se_cmd, shutdown);
 		if (!rc && shutdown && se_cmd && se_cmd->se_sess) {
 			__iscsit_free_cmd(cmd, true, shutdown);
 			target_put_sess_cmd(se_cmd->se_sess, se_cmd);
@@ -752,7 +752,7 @@ void iscsit_free_cmd(struct iscsi_cmd *cmd, bool shutdown)
 			se_cmd = &cmd->se_cmd;
 			__iscsit_free_cmd(cmd, true, shutdown);
 
-			rc = transport_generic_free_cmd(&cmd->se_cmd, 1);
+			rc = transport_generic_free_cmd(&cmd->se_cmd, shutdown);
 			if (!rc && shutdown && se_cmd->se_sess) {
 				__iscsit_free_cmd(cmd, true, shutdown);
 				target_put_sess_cmd(se_cmd->se_sess, se_cmd);