Remove special case handling of "ro." properties permissions

Currently, properties that begin with "ro." are special cased to skip
over the "ro." part of the prefix before matching with entries in
property_contexts.  This is not strictly needed however and it is
causing complications with the separated prop files work from Bug
21852512, so it is now removed.

Bug 26425619

Change-Id: I3cd14fa2176f96b3931e5f6a50c4a7bcd3af3da6