iscsi-target: Add missing CMDSN_LOWER_THAN_EXP check in iscsit_handle_scsi_cmd

This patch adds a missing CMDSN_LOWER_THAN_EXP return check for
iscsit_sequence_cmd() in iscsit_handle_scsi_cmd() that was incorrectly
dropped during the v3.1-rc cleanups to use iscsit_sequence_cmd().

Cc: Andy Grover <agrover@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/iscsi/iscsi_target.c

@@ -1079,7 +1079,9 @@ attach_cmd:
 	 */
 	if (!cmd->immediate_data) {
 		cmdsn_ret = iscsit_sequence_cmd(conn, cmd, hdr->cmdsn);
-		if (cmdsn_ret == CMDSN_ERROR_CANNOT_RECOVER)
+		if (cmdsn_ret == CMDSN_LOWER_THAN_EXP)
+			return 0;
+		else if (cmdsn_ret == CMDSN_ERROR_CANNOT_RECOVER)
 			return iscsit_add_reject_from_cmd(
 				ISCSI_REASON_PROTOCOL_ERROR,
 				1, 0, buf, cmd);