Users that are attached to a Kerberos realm do not have shadow data
on the system. This breaks two accounts-related tasks.
This patch cause Ansible to skip over any users that do not have
shadow data on the system. Without this patch, the playbook fails
with an error.
Closes-Bug: 1659232
Change-Id: Ibbd275681e65ba7ccfc4477caa499247ed052649