Make Akka client test more stable

We already have a hack to wait for client span to close after the
request because it is closed on separate thread. This patch extends
that hack to handle cases when original request throws an exception.

dd-java-agent/instrumentation/akka-http-10.0/src/test/groovy/AkkaHttpClientInstrumentationTest.groovy

@@ -23,8 +23,12 @@ class AkkaHttpClientInstrumentationTest extends HttpClientTest<AkkaHttpClientDec
       .withMethod(HttpMethods.lookup(method).get())
       .addHeaders(headers.collect { RawHeader.create(it.key, it.value) })
 
-    def response = Http.get(system).singleRequest(request, materializer).toCompletableFuture().get()
+    def response
+    try {
+      response = Http.get(system).singleRequest(request, materializer).toCompletableFuture().get()
+    } finally {
       blockUntilChildSpansFinished(1)
+    }
     callback?.call()
     return response.status().intValue()
   }