fix(JingleSessionPC): Disable unified-plan for p2p.

Disable cross browser p2p using unified plan until all the issues are fixed.

JitsiConference.js

@@ -1929,7 +1929,7 @@ JitsiConference.prototype._onIncomingCallP2P = function(
 
     let rejectReason;
 
-    if (!this.isP2PEnabled() && !this.isP2PTestModeEnabled()) {
+    if (!this.isP2PEnabled() && !this.isP2PTestModeEnabled() && (browser.isFirefox() || browser.isWebKitBased())) {
         rejectReason = {
             reason: 'decline',
             reasonDescription: 'P2P disabled',
@@ -3193,7 +3193,7 @@ JitsiConference.prototype._suspendMediaTransferForJvbConnection = function() {
  * @private
  */
 JitsiConference.prototype._maybeStartOrStopP2P = function(userLeftEvent) {
-    if (!this.isP2PEnabled() || this.isP2PTestModeEnabled()) {
+    if (!this.isP2PEnabled() || this.isP2PTestModeEnabled() || browser.isFirefox() || browser.isWebKitBased()) {
         logger.info('Auto P2P disabled');
 
         return;

modules/xmpp/JingleSessionPC.js

@@ -337,7 +337,7 @@ export default class JingleSessionPC extends JingleSession {
             = browser.supportsUnifiedPlan()
                 && (browser.isFirefox()
                     || browser.isWebKitBased()
-                    || (browser.isChromiumBased() && options.enableUnifiedOnChrome));
+                    || (!this.isP2P && browser.isChromiumBased() && options.enableUnifiedOnChrome));
 
         if (this.isP2P) {
             // simulcast needs to be disabled for P2P (121) calls