Fix intermittently failing unit test.

- This test fails if you haven't switched the phone screen on, which
  can be very confusing if you don't know about it.
- This cl introduces acquiring and releasing the screen wake lock to
  the integration test utils, and uses it to prevent this test failure.

Change-Id: I378b6effd56e912213eb0af81f8add5c3bba39f2
2 files changed