Mark task as failed if benchmark validation fails

Closes-Bug: #1276826
Change-Id: Idab924ab51cdd30c232b620abf161af40f3e4ac2

rally/benchmark/engine.py

@@ -146,6 +146,7 @@ class TestEngine(object):
                                                    "validation":
                                                    {"is_valid": False,
                                                     "exc_msg": e.message}})
+                    self.task.set_failed()
                     LOG.error(_("Scenario (%(pos)s, %(name)s) input arguments "
                                 "validation error: %(msg)s") %
                               {"pos": n, "name": name, "msg": e.message})

tests/benchmark/test_engine.py

@@ -194,6 +194,7 @@ class TestEngineTestCase(test.TestCase):
                                      {'raw': [],
                                       'validation': {'is_valid': False,
                                       'exc_msg': validation_exc.message}}),
+            mock.call.set_failed(),
             mock.call.update_status(s.FINISHED)
         ]
         # NOTE(msdubov): Ignore task['uuid'] calls which are used for logging