response to siprec invite should have a:recvonly if offer had a:sendonly (#298)

lib/utils/siprec-utils.js

@@ -242,7 +242,8 @@ const createSipRecPayload = (sdp1, sdp2, logger) => {
     .replace(/a=sendonly\r\n/g, '')
     .replace(/a=direction:both\r\n/g, '');
   */
-  return combinedSdp;
+
+  return combinedSdp.replace(/sendrecv/g, 'recvonly');
 };
 
 module.exports = { parseSiprecPayload, createSipRecPayload } ;