Change the default StorageClass to the CSI one

On new installations, we should make the StorageClass created by the CSI operator the default one. 

However, we shouldn't do that on an upgrade scenario. The main reason is that users might have set  a different quota on the CSI driver Storage Class.

Exit criteria:

• New clusters get the CSI Storage Class as the default one.
• Existing clusters don't get their default Storage Classes changed.