Find way of dealing with cloud specific settings

[gtema]

We know that certain cloud use certain defaults that should be respected (ipv4/v6, support for features leading to using one way or different way). One of the additional interesting cases is that CSP is able to alter supported image container_format and disk_format. Typically we show supported values in the help strings (here mostly create operation. We should find the way how such configuration can be discovered from the cloud and eventually respected in the help strings (i.e. when help is called without known cloud use the default, otherwise use whatever was previously discovered from that cloud)