A recent bug [0] and fix upstream no longer ensures that we use the
tripleo-admin user as the ansible_ssh_user when invoking ansible
playbooks against the undercloud. This means we need to update the
keytab group to something else. Using root makes sense because the user
invoking the overcloud installation should already have root access.
In addition to changing the group, this patch updates the appropriate
tasks so there run with `become: true`, allowing them to access the
keytab.
[0] https://bugs.launchpad.net/tripleo/+bug/1884123
Partial-Bug: 1886870
Change-Id: I523d17f48b8e49e28a1b3becfd5e0cdf044ff742
d3d47118db