[hotfix] Remove akka dependency in MetricUtilsTest

Author: zentol

flink-runtime/src/test/java/org/apache/flink/runtime/metrics/util/MetricUtilsTest.java

@@ -28,7 +28,6 @@
 import org.apache.flink.runtime.metrics.MetricNames;
 import org.apache.flink.runtime.rpc.RpcService;
 import org.apache.flink.runtime.rpc.RpcSystem;
-import org.apache.flink.runtime.rpc.akka.AkkaRpcService;
 import org.apache.flink.runtime.taskexecutor.TaskManagerServices;
 import org.apache.flink.runtime.taskexecutor.TaskManagerServicesBuilder;
 import org.apache.flink.runtime.taskexecutor.slot.TestingTaskSlotTable;
@@ -40,7 +39,6 @@
 
 import org.apache.flink.shaded.guava18.com.google.common.collect.Sets;
 
-import akka.actor.ActorSystem;
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.Assume;
@@ -54,7 +52,6 @@
 import static org.apache.flink.runtime.metrics.util.MetricUtils.METRIC_GROUP_FLINK;
 import static org.apache.flink.runtime.metrics.util.MetricUtils.METRIC_GROUP_MANAGED_MEMORY;
 import static org.apache.flink.runtime.metrics.util.MetricUtils.METRIC_GROUP_MEMORY;
-import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
 
@@ -83,17 +80,10 @@ public void testStartMetricActorSystemRespectsThreadPriority() throws Exception
         final RpcService rpcService =
                 MetricUtils.startRemoteMetricsRpcService(
                         configuration, "localhost", RpcSystem.load());
-        assertThat(rpcService, instanceOf(AkkaRpcService.class));
-
-        final ActorSystem actorSystem = ((AkkaRpcService) rpcService).getActorSystem();
 
         try {
             final int threadPriority =
-                    actorSystem
-                            .settings()
-                            .config()
-                            .getInt("akka.actor.default-dispatcher.thread-priority");
-
+                    rpcService.execute(() -> Thread.currentThread().getPriority()).get();
             assertThat(threadPriority, is(expectedThreadPriority));
         } finally {
             rpcService.stopService().get();