Description of problem:
Gear create (app-create call over mcollective) generates a new ssh key that gets absorbed by mongo at the app level.
Issue is nobody deletes it when gear-destroy is called.

Background : Broker understands that app ssh key can be added by a cartridge which may forget to delete it. So mechanism was put in place that a component_id will be stored with each app-ssh-key to recall who created it. 
With recent code changes, an app-ssh-key is generated at gear create time, but this means that component-id is null. The fallout is that app's ssh-key list keeps growing because there is no way to delete from it.

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Create scalable app
2. Scale-up/down several times
3.

Actual results:
App ssh keys keep growing in the application's mongo record.

Expected results:
Only components should be allowed to add ssh keys to app, or there should be a way to delete the ssh keys added by gears themselves.


Additional info: