exclude testing class from coverage

Author: amarziali

dd-java-agent/testing/build.gradle

@@ -31,6 +31,7 @@ excludedClassesCoverage += [
   'datadog.trace.agent.test.AgentTestRunner',
   'datadog.trace.agent.test.AbortTransformationException',
   'datadog.trace.agent.test.naming.VersionedNamingTestBase',
+  'datadog.trace.agent.test.server.http.HttpProxy.AsyncPipe',
   'datadog.trace.agent.test.server.http.TestHttpServer.*',
   'datadog.trace.agent.test.utils.*',
   // Avoid applying jacoco instrumentation to classes instrumented by tested agent