Use the existence of pending rather than the absence of config.
Check for charm as part of executing retry loop.
Merge pull request #497 from jaycee/check-for-charm-retry

Check for charm as well as service before rendering insepctor

* Use existing retry loop code
* Require charm to be available as well as service (ie model) before rendering
* Drive-by: use the existence of "pending" rather than absence of "config" to
  determine the type of inspector to render.