Enable client certificates in SecureSocket and SecureServerSocket

tests/standalone/io/secure_server_test.dart

Index: tests/standalone/io/secure_server_test.dart
diff --git a/tests/standalone/io/secure_server_test.dart b/tests/standalone/io/secure_server_test.dart
index 89415483b9542d8d49b105715aacb69944818f6f..d27ca9a4effd734298c3efd00956ad47153eda2f 100644
--- a/tests/standalone/io/secure_server_test.dart
+++ b/tests/standalone/io/secure_server_test.dart
@@ -101,7 +101,8 @@ void main() {
   Path scriptDir = new Path.fromNative(new Options().script).directoryPath;
   Path certificateDatabase = scriptDir.append('pkcert');
   SecureSocket.initialize(database: certificateDatabase.toNativePath(),
-                          password: 'dartdart');
+                          password: 'dartdart',
+                          useBuiltinRoots: false);
 
   var server = new SecureTestServer();
   int port = server.start();