Some cleanup for CP2

- Get ContactDirectoryManager's debug flag from sys prop.
- Introduce a debug sys prop to all scan directories.
- Some clean up for voicemail provider too
ContentProvider.getCallingPackage() didn't used to exist, so it has
custom code for that.  Now we can just use getCallingPackage().

Test: adb shell am instrument -w com.android.providers.contacts.tests
Change-Id: Ic16d598251f4bc0bb84b0b71dac2366f195425fe
3 files changed