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

test/get/hosted/cached_pubspec_test.dart

Index: test/get/hosted/cached_pubspec_test.dart
diff --git a/test/get/hosted/cached_pubspec_test.dart b/test/get/hosted/cached_pubspec_test.dart
index 7d3cf086fedc8a47341f8f4f43406d4f3fe412e7..8f1d7d72b2f5f90264afcf9812991c38633c9851 100644
--- a/test/get/hosted/cached_pubspec_test.dart
+++ b/test/get/hosted/cached_pubspec_test.dart
@@ -21,7 +21,7 @@ main() {
     globalServer.clearRequestedPaths();
 
     d.cacheDir({"foo": "1.2.3"}).validate();
-    d.packagesDir({"foo": "1.2.3"}).validate();
+    d.appPackagesFile({"foo": "1.2.3"}).validate();
 
     // Run the solver again now that it's cached.
     pubGet();