Many small YARN improvements.

This pull request fixes some YARN-related bugs:
* Fix temporary directory behavior of YARN and .yarn-jobmanager permissions for different users. #736
* YARN session client should use "fs.hdfs.hadoopconf" if property set in conf #733
* warning if the user is using "file:" as the distributed file system
* Don't show JobManager URL in stratosphere-client if submitting to YARN. 
* Suggested fix for: IllegalMonitorStateException in TaskManager. #739