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

test/get/git/check_out_and_upgrade_test.dart

Index: test/get/git/check_out_and_upgrade_test.dart
diff --git a/test/get/git/check_out_and_upgrade_test.dart b/test/get/git/check_out_and_upgrade_test.dart
index 670ee378dd499a75f4ec6b90a4cd3e9e84decf34..94e7dc1237dfd58eeb1e789564565a9360f98ca6 100644
--- a/test/get/git/check_out_and_upgrade_test.dart
+++ b/test/get/git/check_out_and_upgrade_test.dart
@@ -18,7 +18,7 @@ main() {
 
     d.appDir({"foo": {"git": "../foo.git"}}).create();
 
-    pubGet();
+    pubGet(args: ["--packages-dir"]);
 
     d.dir(cachePath, [
       d.dir('git', [
@@ -38,7 +38,9 @@ main() {
       d.libPubspec('foo', '1.0.0')
     ]).commit();
 
-    pubUpgrade(output: contains("Changed 1 dependency!"));
+    pubUpgrade(
+        args: ["--packages-dir"],
+        output: contains("Changed 1 dependency!"));
 
     // When we download a new version of the git package, we should re-use the
     // git/cache directory but create a new git/ directory.