Allow white-listed apps to change VIBRATE_WHEN_RINGING

We don't allows apps white-listed to write to system
settings to change settings that aren't a part of the
public APIs. Now that we made VIBRATE_WHEN_RINGING it
should be moved from the list of private settings to
the public list which apps can modify.

bug:25941020

Change-Id: Ice91f782aeca4785fa0aed300b22d9ecdbb51bd3