Drop code that is no longer used or no longer required since the move
back to strictly confined snaps.
* Everything is run as root in strict snaps so there's no need
to drop privileges, no need to chown dirs/templates to anything
but root, and the default dir/file modes should suffice.
* copyfiles: we wanted to move away from this and finally did, so
so it's no longer used.
* rchown and rchmod: these are no longer used.
chmod is still used by nova-hypervisor, so let's keep it. I'm not
sure that we still need chown, but I've left that in case we happen
to.
Change-Id: I45be76121b73f0c354a9bcc4014af534455cb533
4544448c83