Add exit_after_auth as an annotation on vault-injector

[plieberg]

Is your feature request related to a problem? Please describe.
Add the 'exit_after_auth' option as a pod annotation. Currently, the only way to use this is to use the configmap method, which adds additional, unwanted complexity to our cronjob deployments.

Describe the solution you'd like
I want the 'exit_after_auth' option to be available as a pod annotation so the agent will exit after authenticating and rendering the template. This is needed so cronjobs that have the vault-injector will exit properly when they have completed executing.

Describe alternatives you've considered
We are currently using the configmap method, but this is a deviation from our developed cronjob standard templates and requires additional work.

Additional context
Add any other context or screenshots about the feature request here.