... and the apparmor.systemd wrapper.

Also add a new 'install-systemd' target to the Makefile to install these
systemd-related files on (open)SUSE by default. Other distributions can
follow by adding a dependency on 'install-systemd' on their
'install-$DISTRO' target.

Note that apparmor.service has ExecStop=/bin/true to avoid that running
processes get unconfined if someone accidently types
    systemctl restart apparmor   (instead of using "reload")

Use aa-teardown if you really want to unload all profiles.

The files in this commit are used in openSUSE since a while, and also in
Arch Linux.

BTW: The condition on var-lib.mount is because openSUSE uses
/var/lib/apparmor/cache/ - but with the changed btrfs layout on
openSUSE, maybe I'll change that to /var/cache/apparmor/ which is
a) used by Debian and b) more sane