Add additional cleanup hook to the app master

Add additional cleanup hook to app master.

Added property mapreduce.job.cleanup.plugins. This property is a list of cleanup plugins that should be run at the end of a job. Each plugin must implement the ApplicationCleanup interface. Plugin classes are specified using mapreduce.job.cleanup.plugins.%s.class properties.

For example:

mapreduce.job.cleanup.plugins=plugin1,plugin2,plugin2 mapreduce.job.cleanup.plugins.plugin1.class=CleanupClass