Fix: Scale down localVideo which is already smaller than requested resolution

(cherry picked from commit a14b3c80ae)

modules/RTC/TraceablePeerConnection.js

@@ -2190,7 +2190,7 @@ TraceablePeerConnection.prototype.setSenderVideoConstraint = function(frameHeigh
                 parameters.encodings[encoding].active = encodingsEnabledState[encoding];
             }
         }
-    } else {
+    } else if (localVideoTrack.resolution > newHeight) {
         parameters.encodings[0].scaleResolutionDownBy = Math.floor(localVideoTrack.resolution / newHeight);
     }