trigger corresponding test workflow

[hougangliu]

for now, we have test workflow for v1alpha2 and v1alpha1, v1alpha1 test workflow should be triggered only when v1alpha1 code changed, so does v1alpha2

[gaocegege]

Agree, we could update https://github.com/kubeflow/katib/blob/master/prow_config.yaml#L32 include_dirs to do it. Could you please help us?