Make "--no-packages-dir" the default.

test/sdk_test.dart

Index: test/sdk_test.dart
diff --git a/test/sdk_test.dart b/test/sdk_test.dart
index 988e7e24706dcb8a599ba576c9bd3f4ae6b6bc14..7c10f74328eb694b2612743d33edcf82f2bd1e12 100644
--- a/test/sdk_test.dart
+++ b/test/sdk_test.dart
@@ -40,8 +40,6 @@ main() {
           'bar': '1.0.0'
         })
       ]).validate();
-
-      d.packagesDir({'foo': '0.0.1', 'bar': '1.0.0'}).validate();
     });
 
     group("fails if", () {
@@ -71,7 +69,7 @@ main() {
                    '- myapp',
             exitCode: exit_codes.UNAVAILABLE);
       });
- 
+
       integration("the SDK doesn't contain the package", () {
         d.appDir({"bar": {"sdk": "flutter"}}).create();
         pubCommand(command,