Simplify MockVpn. am: 4b615c01e5

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/13425310

Change-Id: Iff91a12ced969b34ba28b792e476c945eecdb817
tree: 02a7a51d8f8ab8ae149c1ef864cc420025dab9dd
  1. core/
  2. services/
  3. tests/