`dummy.failure' was the first class-based workload so
it got specific name started with lowercase `dummy'.
But other dummy scenarios have become class-based recently,
so dummy.failure is a kind of white crow now.
This patch simply renames the workload, without keeping
backward compatibility, because this is not critical.
Change-Id: I9ddeb0368adc7e517a74e6d25144b8e88ee4cd44
54f809745f