Set Holo Ringlock Style as default in the Settings app

This NEEDS the respective commit in frameworks/base which sets the default
ringlock style in the class implementing the locker to Holo, too. If the build
is done with just one of these two "pair commits", the observed behavior will
be inconsistent for the user.

Change-Id: Ieaf5bdbb23b967f994830a4d75a48b5fc387eaec