修复simulcast无法开启主码流的问题

www/webrtc/ZLMRTCClient.js

@@ -7399,18 +7399,11 @@ var ZLMRTCClient = (function (exports) {
 	      };
 
 	      if (this.options.simulcast && stream.getVideoTracks().length > 0) {
-	        VideoTransceiverInit.sendEncodings = [{
-	          rid: 'q',
-	          active: true,
-	          scaleResolutionDownBy: 4.0
-	        }, {
-	          rid: 'h',
-	          active: true,
-	          scaleResolutionDownBy: 2.0
-	        }, {
-	          rid: 'f',
-	          active: true
-	        }];
+			  VideoTransceiverInit.sendEncodings = [
+				  { rid: "h", active: true, maxBitrate: 1000000 },
+				  { rid: "m", active: true, maxBitrate: 500000, scaleResolutionDownBy: 2 },
+				  { rid: "l", active: true, maxBitrate: 200000, scaleResolutionDownBy: 4 }
+			  ];
 	      }
 
 	      if (stream.getAudioTracks().length > 0) {