Speed up ConnectivityServiceTest.

1. Override WakeupMessage with an implementation that uses
   sendEmptyMessageDelayed. This allows us to replace a
   6-second sleep with a 150ms wait.
2. Change waitFor()'s polling interval from 100ms to 50ms.

With these changes ConnectivityServiceTest goes from ~9s to ~3s.

Change-Id: Id78aab9cded90a5b17f09d7f437904e179808dd2