The ceph-ansible tasks are now invoked with the tripleo-admin user,
which doesn't by default have write access to /var/lib/mistral, but it
does have sudo access.
This change makes /var/lib/mistral/overcloud/ceph-ansible be owned by
the tripleo-admin user so that subsequent tasks can write to that
directory.
Related-Bug: #1813832
Change-Id: I98bb38078be84cbda3e9a9e338af0d054dc53420