okhttp: Workaround SSLSocket not noticing socket is closed

Using --runs_per_test=1000, this changes the flake rate of TlsTest from
2% to 0%.

While I believe it is possible to write a reliable test for this
(including noticing the SSLSocket behavior), it was becoming too
invasive so I gave up.

Fixes #11012

okhttp/src/main/java/io/grpc/okhttp/OkHttpServerTransport.java

@@ -50,6 +50,7 @@
 import io.grpc.okhttp.internal.framed.Variant;
 import java.io.IOException;
 import java.net.Socket;
+import java.net.SocketException;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -170,6 +171,13 @@ private void startIo(SerializingExecutor serializingExecutor) {
       HandshakerSocketFactory.HandshakeResult result =
           config.handshakerSocketFactory.handshake(socket, Attributes.EMPTY);
       synchronized (lock) {
+        if (socket.isClosed()) {
+          // The wrapped socket may not handle the underlying socket being closed by shutdown(). In
+          // particular, SSLSocket hangs future reads if the underlying socket is already closed at
+          // this point, even if you call sslSocket.close() later.
+          result.socket.close();
+          throw new SocketException("Socket close raced with handshake");
+        }
         this.socket = result.socket;
       }
       this.attributes = result.attributes;