scw create leaves an unattached volume on failure

[djalal]

Related to #534, there is an annoying side-effect.

If I go to the "Volumes" tab, or list scw images -a -f "type=volume", there is an ever growing list of volumes, each time a failed scw create command is issued.

Removing them by hand is still slow, there is no _volumes command to my knowledge :/

Expected behavior

don't provision volumes, ips unless we can deliver a full new server

[kindermoumoute]

This will be solved with #546