Create a safeguard to kill errant recursive workflows before they bring down oozie

If a user creates an errant workflow with a sub-workflow that calls the workflow again, without a proper decision node to exit the workflow, it will continue to create numerous jobs until the oozie server is saturated. A user recently had 400,000 running jobs and oozie was non-responsive. I would suggest we have some method of preventing a user from taking out oozie, such as a max running jobs
parameter.