chore(test): update ITStorageTest to explicitly shutdown the grpc channel for KMS (#1379)

Refactor afterClass() to attempt cleanup of each resource independently

Explicitly shutting down the grpc channel for KMS prevents the following exception from error being reported

```
*~*~*~ Channel ManagedChannelImpl{logId=1, target=cloudkms.googleapis.com:443} was not shutdown properly!!! ~*~*~*
    Make sure to call shutdown()/shutdownNow() and wait until awaitTermination() returns true.
java.lang.RuntimeException: ManagedChannel allocation site
	at io.grpc.internal.ManagedChannelOrphanWrapper$ManagedChannelReference.<init>(ManagedChannelOrphanWrapper.java:93)
	at io.grpc.internal.ManagedChannelOrphanWrapper.<init>(ManagedChannelOrphanWrapper.java:53)
	at io.grpc.internal.ManagedChannelOrphanWrapper.<init>(ManagedChannelOrphanWrapper.java:44)
	at io.grpc.internal.ManagedChannelImplBuilder.build(ManagedChannelImplBuilder.java:630)
	at io.grpc.internal.AbstractManagedChannelImplBuilder.build(AbstractManagedChannelImplBuilder.java:297)
	at com.google.cloud.storage.it.ITStorageTest.prepareKmsKeys(ITStorageTest.java:322)
	at com.google.cloud.storage.it.ITStorageTest.beforeClass(ITStorageTest.java:255)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.RunBefores.invokeMethod(RunBefores.java:33)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runners.Suite.runChild(Suite.java:128)
	at org.junit.runners.Suite.runChild(Suite.java:27)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
	at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
```

Author: BenWhitehead

google-cloud-storage/src/test/java/com/google/cloud/storage/it/ITStorageTest.java

@@ -234,6 +234,8 @@ public class ITStorageTest {
       Notification.PayloadFormat.JSON_API_V1.JSON_API_V1;
   private static final Map<String, String> CUSTOM_ATTRIBUTES = ImmutableMap.of("label1", "value1");
 
+  private static ManagedChannel kmsChannel;
+
   @BeforeClass
   public static void beforeClass() throws IOException {
     remoteStorageHelper = RemoteStorageHelper.create();
@@ -276,13 +278,27 @@ private static void unsetRequesterPays() {
 
   @AfterClass
   public static void afterClass() throws ExecutionException, InterruptedException {
-    if (storage != null) {
+    if (kmsChannel != null) {
+      try {
+        kmsChannel.shutdownNow();
+      } catch (Exception e) {
+        log.log(Level.WARNING, "Error while trying to shutdown kms channel", e);
+      }
+      kmsChannel = null;
+    }
 
-      /* Delete the Pub/Sub topic */
-      if (topicAdminClient != null) {
+    /* Delete the Pub/Sub topic */
+    if (topicAdminClient != null) {
+      try {
         topicAdminClient.deleteTopic(TOPIC);
         topicAdminClient.close();
+      } catch (Exception e) {
+        log.log(Level.WARNING, "Error while trying to delete topic and shutdown topic client", e);
       }
+      topicAdminClient = null;
+    }
+
+    if (storage != null) {
       // In beforeClass, we make buckets auto-delete blobs older than a day old.
       // Here, delete all buckets older than 2 days. They should already be empty and easy.
       long cleanTime = System.currentTimeMillis() - TimeUnit.DAYS.toMillis(2);
@@ -312,8 +328,7 @@ private static void prepareKmsKeys() throws IOException {
     // https://cloud.google.com/storage/docs/encryption/using-customer-managed-keys
     String projectId = remoteStorageHelper.getOptions().getProjectId();
     GoogleCredentials credentials = GoogleCredentials.getApplicationDefault();
-    ManagedChannel kmsChannel =
-        ManagedChannelBuilder.forTarget("cloudkms.googleapis.com:443").build();
+    kmsChannel = ManagedChannelBuilder.forTarget("cloudkms.googleapis.com:443").build();
     KeyManagementServiceBlockingStub kmsStub =
         KeyManagementServiceGrpc.newBlockingStub(kmsChannel)
             .withCallCredentials(MoreCallCredentials.from(credentials));