See the workarounds for Debian 8 & Ubuntu 16.04 here:
https://www.redhat.com/archives/libguestfs/2016-October/msg00099.html
I tested password changing and that's working fine.
Rich.
--
Richard Jones, Virtualization Group, Red Hat
http://people.redhat.com/~rjones
Read my programming and virtualization blog:
http://rwmj.wordpress.com
virt-top is 'top' for virtual machines. Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top