Restructure platform test setup
Current setup sucks for various reasons:
- testing hosts are tied to vagrant
- leap_cli, provider config and hosts need to be on one machine
- greyhound is at its mem limits
Much better would be:
- integrate fog into leap_cli so we can start/stop/destroy remote hosts from leap_cli
- ability to import provider config from single (json) file
(from redmine: created on 2016-01-27, closed on 2016-11-08, relates #7845)