Fix ExtServices tests

- Switch the tests from Android.mk to Android.bp. The app itself
cannot move over yet because it uses syntax not supported by bp
- Instrument the test package instead of the package udner test
- Also fix an actual error in a test

Test: this
Change-Id: I0af081ab25630e4e911d4d9cbb60a87b2f75be90
Fixes: 123572762