Adding new umbilical protocol RPC, getAggregationTargets, for node-level combiner.

Signed-off-by: OZAWA <ozawa.tsuyoshi@lab.ntt.co.jp>
Adding aggregationWaitMap for node-level combiner.

Signed-off-by: OZAWA <ozawa.tsuyoshi@lab.ntt.co.jp>
Adding AggregationWaitMap to some components(MRAppMaster, TaskAttemptListener, JobImpl, MapTaskImpl).

Signed-off-by: OZAWA <ozawa.tsuyoshi@lab.ntt.co.jp>
Changed Mappers and Reducers to support Node-level aggregation

Signed-off-by: OZAWA <ozawa.tsuyoshi@lab.ntt.co.jp>
Fixed to add failure handling when MapTask fails

Signed-off-by: Tsuyoshi Ozawa <ozawa.tsuyoshi@gmail.com>
Add node-level aggregation configrations to Job/JobConf(MAPREDUCE-4911)

Signed-off-by: Tsuyoshi Ozawa <ozawa.tsuyoshi@lab.ntt.co.jp>