Pavol, is this present on 5.9 which is what the BZ is marked for. Also, this sounds like a regression, can we look at 5.8.2 and see if this works please.
The following allows to have flavors with disk size of 0 in the drop-down list. Once merged we can back port it to Gaprindashvili (5.9.x) and Fine (5.8.x) branches. https://github.com/ManageIQ/manageiq-providers-openstack/pull/314
The feature has been merged upstream and can be back ported to 5.9.x and 5.8.x.
Verified ======== 5.10.0.23