Implements pillar key defining volume backend driver (volume_driver)

Reclass model example to set driver class:

cinder:
  controller:
    backend:
      FJISCSI:
        driver: cinder.volume.drivers.fujitsu.eternus_dx.eternus_dx_iscsi.FJDXISCSIDriver
        engine: fujitsu

Change-Id: Idc0bc5c49ba08161333742d8c3bb171023eb5415
Closes-Bug: PROD-30853
Related-Prod: PROD-30853
2 files changed