Merge pull request #8963 from ctiller/fixit31

Interop test might take a little longer to start up (esp. w/tsan)
diff --git a/test/cpp/interop/interop_test.cc b/test/cpp/interop/interop_test.cc
index c066598..d400474 100644
--- a/test/cpp/interop/interop_test.cc
+++ b/test/cpp/interop/interop_test.cc
@@ -126,7 +126,7 @@
     return 1;
   }
   /* wait a little */
-  sleep(2);
+  sleep(10);
   /* start the clients */
   ret = test_client(root, "127.0.0.1", port);
   if (ret != 0) return ret;