Older version of openstack did not worked with gcow2 glance images properly in all the cases (for ex. ceph, direct backend). The newer ones (some cases) needs to do an extra conversion which makes the boot slower, so it is better to upload raw images to glance.
https://access.redhat.com/solutions/2434691 'It is always better to upload raw images if Ceph is backend for glance. '
python-tempestconf's version 2.2.0 contains the requested feature and it's included in python-tempestconf-2.2.0-1.el7ost package which is now available via the latest symlink in RHOS-13 repository.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2019:1739