try to fix netty test

Author: amarziali

dd-java-agent/instrumentation/netty-4.1/src/test/groovy/Netty41ServerTest.groovy

@@ -175,6 +175,7 @@ abstract class Netty41ServerTest extends HttpServerTest<EventLoopGroup> {
                 it.flush()
               },
               userEventTriggered : { ChannelHandlerContext ctx, Object evt ->
+                System.out.println("Received event $evt. session is ${WsEndpoint.activeSession}")
                 if (evt instanceof WebSocketServerProtocolHandler.HandshakeComplete) {
                   WsEndpoint.onOpen(ctx)
                 }
@@ -285,6 +286,10 @@ abstract class Netty41ServerTest extends HttpServerTest<EventLoopGroup> {
   boolean testBadUrl() {
     false
   }
+
+  def cleanup() {
+    WsEndpoint.activeSession = null
+  }
 }
 
 class Netty41ServerV0Test extends Netty41ServerTest implements TestingNettyHttpNamingConventions.ServerV0 {
@@ -310,5 +315,3 @@ class WsEndpoint {
     activeSession = null
   }
 }
-
-