enable/disable/stop a worker

def _worker_ctl(worker, lbn, vwa, profile='default'):
    '''
    enable/disable/stop a worker
    '''

    cmd = {
        'cmd': 'update',
        'mime': 'prop',
        'w': lbn,
        'sw': worker,
        'vwa': vwa,
    }
    return _do_http(cmd, profile)['worker.result.type'] == 'OK'