Openstack provider backend support

- Major lintage happened (see below), the main functional change
  is the addition of OpenstackEC2System
- OpenstackEC2System comes with a lot of gotchas, see its
  docstring for more info
- Stubbed support for 'can_suspend' checking in power control
  tests

Lint/pep8 pass info:
  - Removed redundant docstrings
  - v6 support in the vmware provider's _find_ip method was an
    egregious violator of style, plus we couldn't do anything
    with a v6 address even if we found one. (:sob:)
    That method is back to only doing ipv4 now.