Remove repeated conditional judgments. (#2068)

tunnel-server/src/main/java/com/alibaba/arthas/tunnel/server/RelayHandler.java

@@ -36,12 +36,10 @@ public final class RelayHandler extends ChannelInboundHandlerAdapter {
 
     @Override
     public void channelInactive(ChannelHandlerContext ctx) {
-        if (relayChannel.isActive()) {
         if (relayChannel.isActive()) {
             relayChannel.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
         }
     }
-    }
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {