config: add flag to disable the E2EE support

 This is useful for testing insertable streams related issues.

config.js

@@ -44,6 +44,10 @@ var config = {
     //
 
     testing: {
+        // Disables the End to End Encryption feature. Useful for debugging
+        // issues related to insertable streams.
+        // disableE2EE: false,
+
         // P2P test mode disables automatic switching to P2P when there are 2
         // participants in the conference.
         p2pTestMode: false