create-stack: update heat environment files

* Increase Ceph volume size to 150GB
* Ensure use of ephemeral volumes in small heat CI environment
* Add missing node name to heat IDF
* Bring number of workers in line between small and large heat CI
environments

Change-Id: I68331dc7c4add335b3d16066f1d0c23618c7196b
Signed-off-by: Cian Johnston <cian.johnston@est.tech>
3 files changed