fixes for connectivity manager test suite

* reduced visibility of most util functions in
  ConnectivityManagerTestBase
* reimplemented various waitFor... util function in base class:
  instead of relying on received broadcast and synchronization
  mechanism, we just poll for what we want with a fixed interval
  and a max timeout
* minor style fixes
* removed state transition checks in all test cases of
  ConnectivityManagerMobileTest: since exact state transitions
  are not that interesting, we just care about if we reach a
  particular state and if all network interfaces are in their
  corresponding states
* clarified in comment what each test cases are testing, since
  some of the test case names are not very straightforward
* any wait for DISCONNECTED checkes with ConnectivityManager are
  temporarily commented out

Change-Id: I99cca95c33c6060909e0df684969b75c2dca23a9