[test] use emptyDir for mysql and minio (#759)
[test] use emptyDir for mysql and minio (#759)

for testing, no persistent storage is needed.
Use `emptyDir:{}` for minio and mysql

Signed-off-by: Yihong Wang <f520643bf8cff572a9eb593b2aa4ab3c892470e2@ibm.com>
kubeflow/kfp-tekton,kubeflow/kfp-tekton,kubeflow/kfp-tekton,kubeflow/kfp-tekton,kubeflow/kfp-tekton,kubeflow/kfp-tekton