Capacity scheduler to re-populate container allocation state

YARN-1367 and YARN-1368 enable the NM to tell the RM about currently running containers and the RM will pass this information to the schedulers along with the node information. The schedulers are currently already informed about previously running apps when the app data is recovered from the store. The scheduler is expected to be able to repopulate its allocation state from the above 2 sources of information.