Create logic for applying padding only to custom preference layouts

n the case of any standard PreferenceFragment layout, we can
change the list styling to add padding and set clipToPadding to false.
In this case, we don't want extra padding in the parent ViewGroup
(R.id.prefs).
When an app specifies a custom preference fragment layout, we want
to add the previously existing padding styles R.id.prefs.

Change-Id: Idfd77dcbef264c6f5f4121b66fd54c684ad0a288