Superset PVC error on moc

[HumairAK]

Superset is running into the following error on MOC:

running "VolumeBinding" filter plugin for pod "superset-1-f9zll": pod has unbound immediate PersistentVolumeClaims

The PVC shows the following error:

superset-data:
no persistent volumes available for this claim and no storage class is set

I'm guessing this is related to #22 - where JH had similar issues. But superset component doesn't seem to give the same method to change storage class via a parameter. We should try overriding this for now. If it works, suggest upstream to add a parameter to specify storage class.

[HumairAK]

Notified upstream here to include storage class as a parameter. In the meantime we'll be overriding it.