fix: Do not send trickle candidates to jicofo (#2149)

The candidates are not necessary when we use jvb.

modules/xmpp/JingleSessionPC.js

                     });
                 this._gatheringReported = true;
             }
-            this.sendIceCandidate(candidate);
+            if (this.isP2P) {
+                this.sendIceCandidate(candidate);
+            }
         };
 
         // Note there is a change in the spec about closed: