The patch adds the backend driver to support iSCSI format storage pools
and volumes for ESX host. The mapping of ESX iSCSI specifics to Libvirt
is as follows:

1. ESX static iSCSI target <------> Libvirt Storage Pools
2. ESX iSCSI LUNs          <------> Libvirt Storage Volumes.

The above understanding is based on http://libvirt.org/storage.html.

The operation supported on iSCSI pools includes:

1. List storage pools & volumes.
2. Get XML descriptor operaion on pools & volumes.
3. Lookup operation on pools & volumes by name, UUID and path (if applicable).

iSCSI pools does not support operations such as: Create / remove pools
and volumes.