feat: implement the driver status hook

[tas50]

kitchen list had nothing to report for this driver beyond what the state file remembered, because Kitchen::Driver::Base#status was never overridden.

def status(state)
  return super unless state[:server_id]

  server = lookup_server(state[:server_id])
  return super unless server
  ...
end

Nova is now asked directly, so a server that was deleted out from under Test Kitchen, or is stuck in BUILD, or has gone to ERROR, is visible without a converge.

live is true only for ACTIVE, matching fog's own ready?.

Three cases fall back to the base "unknown" answer rather than raising, because kitchen list should never blow up on a driver it is merely interrogating: no server in state, Nova does not know the id, and the cloud cannot be reached. The lookup honours disable_ssl_validation the same way create and destroy do.

A note on super

Kitchen::Driver::Base#status only exists in Test Kitchen 4.1.0 and later, and only 4.1.0+ calls driver.status, so the super calls are unreachable on a version that lacks them. This matches the pattern already in kitchen-cloudstack, kitchen-ec2, and kitchen-google.

Verification

• rake test — 367 examples, 0 failures (360 before; 7 new), rake exit 0
• cookstyle --chefstyle — 11 files, no offenses
• yard stats — 100% documented