Adds xiv_ds8k cinder driver support

To use xiv_ds8k, set the following in localrc:
CINDER_ENABLED_BACKENDS+=,xiv:<volume-type-name>
XIV_DRIVER_VERSION=<version-string>
SAN_IP=<storage-ip-or-hostname>
SAN_LOGIN=<storage-admin-account>
SAN_PASSWORD=<storage-admin-password>
SAN_CLUSTERNAME=<cluster-name>
CONNECTION_TYPE=<connection-type> iscsi|fc
XIV_CHAP=<chap-type> disabled|enabled

Change-Id: I084ad2b2cb8e34c4a8aed77a52e90f9a9739f1f3
Merge "Adds xiv_ds8k cinder driver support"