apparmor: Make abstractions extensible

Implement the standard AppArmor 3.x abstraction extension
approach.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Jim Fehlig <jfehlig@suse.com>

src/security/apparmor/libvirt-lxc.in

@@ -116,3 +116,7 @@
   deny /sys/fs/cgrou[^p]*{,/**} wklx,
   deny /sys/fs/cgroup?*{,/**} wklx,
   deny /sys/fs?*{,/**} wklx,
+
+@BEGIN_APPARMOR_3@
+  include if exists <abstractions/libvirt-lxc.d>
+@END_APPARMOR_3@

src/security/apparmor/libvirt-qemu.in

@@ -271,3 +271,7 @@
   # required for QEMU accessing UEFI nvram variables
   owner /var/lib/libvirt/qemu/nvram/*_VARS.fd rwk,
   owner /var/lib/libvirt/qemu/nvram/*_VARS.ms.fd rwk,
+
+@BEGIN_APPARMOR_3@
+  include if exists <abstractions/libvirt-qemu.d>
+@END_APPARMOR_3@