Support setting the default interface to null again. am: bbb550ceb7 am: b9a2ef98d9

Change-Id: I957babd740b0cef5f437467af7ebcac5fb373350
tree: 0a2fec897425377986fe2e17fa9d6aac054a0a28
  1. java/
  2. tests/
  3. .gitignore
  4. Android.bp