Fixed endless loop when used endpoint with RFC 5438 support

kamailio/default.cfg

@@ -474,6 +474,9 @@ route[HANDLE_MESSAGE]
             if( $hdr(Content-Type) == "application/im-iscomposing+xml" ) {
                 xlog("L_WARN", "$ci|end|dropping MESSAGE application/im-iscomposing+xml\n");
                 sl_send_reply("200", "OK");
+            } else if( $hdr(Content-Type) == "message/imdn+xml" ) {
+                xlog("L_WARN", "$ci|end|dropping MESSAGE message/imdn+xml\n");
+                sl_send_reply("202", "Accepted");
             } else {
                 route(DISPATCHER_FIND_ROUTES);
                 route(EXTERNAL_TO_INTERNAL_RELAY);