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

test/upgrade/git/upgrade_one_locked_test.dart

Index: test/upgrade/git/upgrade_one_locked_test.dart
diff --git a/test/upgrade/git/upgrade_one_locked_test.dart b/test/upgrade/git/upgrade_one_locked_test.dart
index d6819ef2663cb3ee471435d46e0229755cf58ea7..5d071328c7851f3a0cd949fd6ea60459573b3b87 100644
--- a/test/upgrade/git/upgrade_one_locked_test.dart
+++ b/test/upgrade/git/upgrade_one_locked_test.dart
@@ -24,7 +24,9 @@ main() {
       "bar": {"git": "../bar.git"}
     }).create();
 
-    pubGet();
+    // TODO(rnystrom): Remove "--packages-dir" and validate using the
+    // ".packages" file instead of looking in the "packages" directory.
+    pubGet(args: ['--packages-dir']);
 
     d.dir(packagesPath, [
       d.dir('foo', [
@@ -45,7 +47,9 @@ main() {
       d.libPubspec('bar', '1.0.0')
     ]).commit();
 
-    pubUpgrade(args: ['foo']);
+    // TODO(rnystrom): Remove "--packages-dir" and validate using the
+    // ".packages" file instead of looking in the "packages" directory.
+    pubUpgrade(args: ['--packages-dir', 'foo']);
 
     d.dir(packagesPath, [
       d.dir('foo', [