Revert "AppSchedulable: Cache list of existing predictions for 'current' and 'future' as long as no allocations are made."

This reverts commit 842fca0cd1367eed9326b5cd3d85a26475c276eb.

Conflicts:

hadoop-2.3.0-src/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AppSchedulable.java