IBM XIV and DS8000 Driver reorganizing (IBM dir)

    * renamed:    cinder/volume/drivers/xiv_ds8k.py
                  -> cinder/volume/drivers/ibm/xiv_ds8k.py
    * updated all references to old xiv_ds8k paths
    * regenerated sample.conf

Change-Id: Iab094c78a0e4eb1753fe8809089ba1337d95e2e0
Partially implements: blueprint ibm-volume-driver-reorg
Merge "IBM XIV and DS8000 Driver reorganizing (IBM dir)"