Cinder had config options to customize the RPC topics on which the
scheduler, volume and backup nodes listen. But this feature has been
dysfunctional for quite a long time. This commit removed this feature.
For more details: Refer the bug comments.
DocImpact
Change-Id: Ie76f070fe9a1222c209e8defd0d04fa7a7931b14
Closes-Bug: #1301888