Make the analysis server integration tests driver only.

pkg/analysis_server/test/integration/analysis/get_reachable_sources_test.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:io';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ skipping 28 matching lines @@
     Map<String, List<String>> sources = result.sources;
     List<String> keys = sources.keys.toList();
     String url = new File(pathname).uri.toString();
 
     expect(keys, contains('dart:core'));
     expect(keys, contains('dart:collection'));
     expect(keys, contains('dart:math'));
     expect(keys, contains(url));
     expect(sources[url], contains('dart:core'));
   }
-
-  @override
-  bool get enableNewAnalysisDriver => true;
 }