Comment 5 for bug 1546674

My 3 updated Xenial machines are still affected by this. Since comment #3, I also added /etc/gai.conf so the new diff looks like this:

$ diff -Naur /etc/apparmor.d/usr.lib.libvirt.virt-aa-helper{.orig,}
--- /etc/apparmor.d/usr.lib.libvirt.virt-aa-helper.orig 2016-08-14 10:32:27.051646248 -0400
+++ /etc/apparmor.d/usr.lib.libvirt.virt-aa-helper 2016-08-17 17:06:33.329358438 -0400
@@ -66,4 +66,10 @@
   /**.vmdk r,
   /**.[iI][sS][oO] r,
   /**/disk{,.*} r,
+
+ # XXX: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1546674
+ /etc/gai.conf r,
+ /etc/hosts r,
+ /etc/host.conf r,
+ /etc/nsswitch.conf r,
 }

I'm attaching a guest definition that triggers the bug hoping to help you reproduce it. If I can be of more help, please let me know.