[cinder-csi-plugin] ephemeral volume removal

[sergelogvinov]

Disable creating new deprecated ephemeral volumes

What this PR does / why we need it:

Remove deprecated ephemeral volumes.

Which issue this PR fixes(if applicable): fixes #2599

Special notes for reviewers:

Hi, @dulek i've disabled only ephemeral volume creation stage. What do you think, we should remove all code or make it in two steps (releases)?

Thanks.

Release note:

In-line ephemeral is no longer available.