remove asymmetric flag on offer to B party reinvite as port learning should still happen (#128)

lib/call-session.js

@@ -775,6 +775,8 @@ Duration=${payload.duration} `
         sdp
       };
       response = await this.answer(opts);
+      /* now remove asymeetric as B party (looking at you Genesys ring group) may need port re-learning on invites  */
+      answerMedia.flags = answerMedia.flags.filter((f) => f !== 'asymmetric');
       if ('ok' !== response.result) {
         res.send(488);
         throw new Error(`_onReinvite: rtpengine failed: ${JSON.stringify(response)}`);