devcg: save locally saved settings

Whenever writing rules in the current directory, save these rules so it
can be used whenever parent's rules change. This patch prepares for
revalidating the local rules based on parent's current state, which is
not only needed to retain whenever possible the local settings but to
allow moving the group to another part of the tree.

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>
devcg: try to reapply local settings

Whenever there's a change in parent's rules, try to apply the locally
set rules. For now, local and parent's behavior must match.

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>