Add automatic creation and deletion of Purity hosts for PureISCSIDriver

The driver will now be responsible to manage hosts for new initiators
which do not already have a host created for them. This will allow for
backwards compatibility with the previous version that relied on hosts
being pre-configured for use by Cinder.


Implements: blueprint pure-iscsi-automatic-host-creation
Change-Id: I04b554e1a21128d55eddc21afda7108a868e4248
Merge "Add automatic creation and deletion of Purity hosts for PureISCSIDriver"