when releasing media, use asymetric flag so that rtpengine does react to a spurious final packet from freeswitch by incorrectly sending rtp there

lib/call-session.js

@@ -552,6 +552,7 @@ Duration=${payload.duration} `
       if (reason && dlg.type === 'uas' && ['release-media', 'anchor-media'].includes(reason)) {
         this.logger.info(`got a reinvite from FS to ${reason}`);
         sdp = dlg.other.remote.sdp;
+        answerMedia.flags = ['asymmetric', 'port latching'];
       }
       else {
         sdp = await dlg.other.modify(response.sdp);