apparmor: add local include for libvirt-qemu & libvirt-lxc

We have had local includes for libvirtd and virt-aa-helper, but
unfortunately the most likely place for local includes to take place is
in /etc/apparmor/abstractions/libvirt-qemu (and libvirt-lxc) where we have
had no such local include yet.

This adds the include to the patch that addes the other Distro specific
includes d/p/debian/apparmor_profiles_local_include.patch.

Furthermore "normal" dh_apparmor can't handle subdirs in the profile
reference (since this is actually an abstraction it has the subdir).
Also for the abstraction we don't want the usual reload code.
Therefore we extract and add just what we need of a dh_apparmor snippet
and add it to the postinst of libvirt-daemon-system.

Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>