(1) Prevent full restore from creating files/directories that are
accessible by other applications
(2) Don't restore filesets from "system" packages; i.e. any that runs
as a special uid, unless they define their own agent for handling
the restore process.
Bug 7168284
This is a cherry-pick from the originating tree.
Change-Id: I9f39ada3c4c3b7ee63330b015e62745e84ccb58f
64d1f3efd7