security: aa-helper: allow virt-aa-helper to read .vhd images

VHD images can be used as any other, so we should add them to the list
of types that virt-aa-helper can read when creating the per-guest rules
for backing files.
Signed-off-by: NChristian Ehrhardt <christian.ehrhardt@canonical.com>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>
Acked-by: NJamie Strandboge <jamie@canonical.com>

src/security/apparmor/usr.lib.libvirt.virt-aa-helper

@@ -63,6 +63,7 @@ profile virt-aa-helper /usr/{lib,lib64}/libvirt/virt-aa-helper {
   /**.qcow{,2} r,
   /**.qed r,
   /**.vmdk r,
+  /**.vhd r,
   /**.[iI][sS][oO] r,
   /**/disk{,.*} r,