reverse implementtion of APP_IMMUNITY

[krishnaghatti]

I was looking at the possibility to have the reverse functionality of APP_IMMUNITY. Say app cop will only check apps that have a certain flag set. Instead of setting APP_IMMUNITY to a lot of apps, only certain apps will be monitored for the frequency of the events.

Use case:
If some of the apps in the cluster are very critical and need to be up and running at any cost, having appcop scale down these containers will serious availability issues to the entire set of services.