For long running services, aggregate logs when a container completes instead of when the app completes

For a long running service, containers will typically not complete very often. However, when a container completes - it would be useful to aggregate the logs right then, instead of waiting for the app to complete.
This will allow the command line log tool to lookup containers for an app from the log file index itself, instead of having to go and talk to YARN. Talking to YARN really only works if ATS is enabled, and YARN is configured to publish container information to ATS (That may not always be the case - since this can overload ATS quite fast).

There's some added benefits like cleaning out local disk space early, instead of waiting till the app completes. (There's probably a separate jira somewhere about cleanup of container for long running services anyway)

cc Vinod Kumar Vavilapalli, Xuan Gong