Fix the broken unit tests

PhoneAccountRegistrarTest is broken, and also non-functional. Get them
updated by fixing proguard (don't strip @VisibleForTesting things),
fixing the setup (need a real ConnectionService), and fixing the tests
themselves to test what PhoneAccountRegistrar does now.

Bug: 17620636
Change-Id: Ibd4d5a4104ff2158b0e7c01a41910f866b94196a