PureISCSIDriver:Handle delete called on already deleted volume

If the delete_volume method gets an error from Purity
saying volume does not exist, don't proceed with attempt
at deletion

Change-Id: I2a830e43c876433da4cdb50eabe4fb66b7eb6faf
Closes-Bug: #1395826
Adding volume driver for X-IO ISE

Driver is implemented using one base class XIOISEDriver and two
classes, one for each storage protocol.

This change also addresses version 1.1.0 of the driver that
adds support for:
- QoS
- Volume affinity
- Thin
- Retype

Driver Cert results:
https://bugs.launchpad.net/cinder/+bug/1360078

Unit test tests all required interfaces for both driver types.

Change-Id: I2eeb44e768871e02e407f93243aabef993f96d53
Implements: blueprint xio-iscsi-fc-volume-driver
Implements: blueprint xio-volume-driver-1-1
Merge "PureISCSIDriver:Handle delete called on already deleted volume"
Merge "Adding volume driver for X-IO ISE"