Comment 6 for bug 1779847

might have a related fix for you (we landed it in tip July 9th) https://bugs.launchpad.net/cloud-init/+bug/1780481

Our nightly builds should have the updates that would work for CentOS 7
https://copr.fedorainfracloud.org/coprs/g/cloud-init/cloud-init-dev/

There is a side-effect of the above fix that I hadn't accounted for on Copr centos 6 where /etc/os-release exists but is an empty file.

There is a subsequent bug that, when fixed, should work on most redhat/cent images.
watch this bug fix for notification of cent6 fixes.
https://bugs.launchpad.net/cloud-init/+bug/1781229