apparmor: Add support for local profile customizations

apparmor: Add support for local profile customizations

Apparmor profiles in /etc/apparmor.d/ are config files that can and should
be replaced on package upgrade, which introduces the potential to overwrite
any local changes. Apparmor supports local profile customizations via
/etc/apparmor.d/local/<service> [1].

This change makes the support explicit by adding libvirtd, virtqemud, and
virtxend profile customization stubs to /etc/apparmor.d/local/. The stubs
are conditionally included by the corresponding main profiles.

[1] https://ubuntu.com/server/docs/security-apparmor
See "Profile customization" section

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>