add missing metric collection when channel becomes inactive

Author: AgraVator

netty/src/main/java/io/grpc/netty/NettyClientHandler.java

@@ -508,6 +508,7 @@ public void channelActive(ChannelHandlerContext ctx) throws Exception {
   public void channelInactive(ChannelHandlerContext ctx) throws Exception {
     try {
       logger.fine("Network channel is closed");
+      tcpMetrics.channelInactive(ctx.channel());
       Status status = Status.UNAVAILABLE.withDescription("Network closed for unknown reason");
       lifecycleManager.notifyShutdown(status, SimpleDisconnectError.UNKNOWN);
       final Status streamStatus;