The fixed value of 20GB root disk for the flavour drop downs [here](https://github.com/stackhpc/azimuth/blob/f222b6183f14cd8f1d1ac5dfac9a49166ae3289e/ui/src/components/pages/tenancy/platforms/kubernetes/form.js#L133) and [here](https://github.com/stackhpc/azimuth/blob/f222b6183f14cd8f1d1ac5dfac9a49166ae3289e/ui/src/components/pages/tenancy/platforms/kubernetes/form.js#L414) shouldn't apply if clusters are using boot from volume.
