interop-testing: Avoid Netty-specific APIs to creating channels

We prefer to test using the stable APIs, as they are what our users
should be using. Http2Client continues using NettyChannelBuilder because
it is intended to test grpc-netty.

interop-testing/src/main/java/io/grpc/testing/integration/Http2Client.java

@@ -23,18 +23,16 @@
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.common.util.concurrent.MoreExecutors;
 import com.google.protobuf.ByteString;
+import io.grpc.ChannelCredentials;
+import io.grpc.InsecureChannelCredentials;
 import io.grpc.ManagedChannel;
 import io.grpc.Status;
 import io.grpc.StatusRuntimeException;
-import io.grpc.netty.NegotiationType;
 import io.grpc.netty.NettyChannelBuilder;
 import io.grpc.stub.StreamObserver;
 import io.grpc.testing.integration.Messages.Payload;
 import io.grpc.testing.integration.Messages.SimpleRequest;
 import io.grpc.testing.integration.Messages.SimpleResponse;
-import java.net.InetAddress;
-import java.net.InetSocketAddress;
-import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
@@ -353,15 +351,8 @@ private void assertResponseEquals(SimpleResponse response, SimpleResponse golden
   }
 
   private ManagedChannel createChannel() {
-    InetAddress address;
-    try {
-      address = InetAddress.getByName(serverHost);
-    } catch (UnknownHostException ex) {
-      throw new RuntimeException(ex);
-    }
-    return NettyChannelBuilder.forAddress(new InetSocketAddress(address, serverPort))
-        .negotiationType(NegotiationType.PLAINTEXT)
-        .build();
+    ChannelCredentials creds = InsecureChannelCredentials.create();
+    return NettyChannelBuilder.forAddress(serverHost, serverPort, creds).build();
   }
 
   private static String validTestCasesHelpText() {

interop-testing/src/main/java/io/grpc/testing/integration/XdsFederationTestClient.java

@@ -20,10 +20,10 @@
 import static org.junit.Assert.assertTrue;
 
 import io.grpc.ChannelCredentials;
+import io.grpc.Grpc;
 import io.grpc.InsecureChannelCredentials;
 import io.grpc.ManagedChannelBuilder;
 import io.grpc.alts.ComputeEngineChannelCredentials;
-import io.grpc.netty.NettyChannelBuilder;
 import java.util.ArrayList;
 import java.util.logging.Logger;
 
@@ -289,7 +289,7 @@ protected ManagedChannelBuilder<?> createChannelBuilder() {
         default:
           throw new IllegalArgumentException("Unknown custom credentials: " + credentialsType);
       }
-      return NettyChannelBuilder.forTarget(serverUri, channelCredentials)
+      return Grpc.newChannelBuilder(serverUri, channelCredentials)
           .keepAliveTime(3600, SECONDS)
           .keepAliveTimeout(20, SECONDS);
     }