Updated de/recommission and "check" scripts to support cdh4 elasticity.

Main changes:
* "Sourcing" a new environment (JTENV) if it is specified
   - need to update it with the correct "vhm-env" file in the future
* Updated parsing of jobtracker stderr file to support DEPRECATED warnings
  - Changed the function parseJTErrFile() and handling its return value

Note: Changes from Serengeti we depend on::
* location of the new environment (/etc/default/hadoop-0.20-mapreduce)
* Enable "root" user to run Hadoop admin commands (e.g., mradmin)
  - added new property mapreduce.cluster.administrators in mapred-site