Description of problem:
The 'status' parameter is mandatory for terminating an external job, however it is not described anywhere.

In addition, even if the status is set, the final status set to the job might not match the one provided by the user.
i.e. if the user asked to terminate a job as 'aborted', it will be marked as 'failed'.

Version-Release number of selected component (if applicable):
4.1.master

How reproducible:
always

Steps to Reproduce:
1. send the following request to terminate a job:

  <action>
    <force>true</force>
  </action>

Actual results:
The request failed due to incomplete parameter.

Expected results:
The model should declare on that parameter.

Additional info:

The 'status' for terminating an external job via the api is mandatory:
(taken from BackendJobResource.java)
public Response end(Action action) {
        validateParameters(action, "status");
  ...
}


However, the model (Job.java) doesn't define such parameter for the end-job request:

interface End {
        @In Boolean force();
        @In Boolean async();
    }