interop-testing: overrideAuthority breaks JWT

Commit 65e4d9f broke the jwt_token_creds. It is believed to be because
the JWT does not see the authority passed to overrideAuthority. So the
changes to interop-testing client are temporarily reverted here. Note
that this breaks GRPC_PROXY_EXP testing, so the incompatibility needs to
be resolved.

Solving #2682 will allow reverting this change.

Fixes grpc/grpc#9497
Fixes #2680

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

@@ -43,6 +43,9 @@
 import io.netty.handler.ssl.SslContext;
 import java.io.File;
 import java.io.FileInputStream;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.UnknownHostException;
 import java.nio.charset.Charset;
 import javax.net.ssl.SSLSocketFactory;
 
@@ -301,6 +304,16 @@ private class Tester extends AbstractInteropTest {
     @Override
     protected ManagedChannel createChannel() {
       if (!useOkHttp) {
+        InetAddress address;
+        try {
+          address = InetAddress.getByName(serverHost);
+          if (serverHostOverride != null) {
+            // Force the hostname to match the cert the server uses.
+            address = InetAddress.getByAddress(serverHostOverride, address.getAddress());
+          }
+        } catch (UnknownHostException ex) {
+          throw new RuntimeException(ex);
+        }
         SslContext sslContext = null;
         if (useTestCa) {
           try {
@@ -310,8 +323,7 @@ protected ManagedChannel createChannel() {
             throw new RuntimeException(ex);
           }
         }
-        return NettyChannelBuilder.forAddress(serverHost, serverPort)
-            .overrideAuthority(serverHostOverride)
+        return NettyChannelBuilder.forAddress(new InetSocketAddress(address, serverPort))
             .flowControlWindow(65 * 1024)
             .negotiationType(useTls ? NegotiationType.TLS : NegotiationType.PLAINTEXT)
             .sslContext(sslContext)