Add tests that try starting the various hadoop command line scripts

Hadoop has lots of tests that start clusters, but I don't see any that test the command line scripts working. Which means that changes to the scripts and the code behind them may not get picked up rapidly, and regressions won't get picked up by Hudson and apportioned to the specific patches.

Propose:

• an abstract test case that can exec scripts on startup; wait for them to finish, kill them if they take too long
• test cases for every service (namenode, tasktracker, datanode, etc)
• tests that try invalid commands, -help options
• tests that start the services, assert that they are live, and shut them down