Fix TelephonyManager to grab the best context

It may not be called from an app so the app context may not exist.
Check and grab the best one.
Also remove the log that nobody paid attention to if the constructor
is called again from the same process.  One context seems to be as
useful as another.

bug:5572369
bug:5622514
Change-Id: Iad23b30c7c8fe5b8d1f81a1e060eaf0cd0e3019d