Add support for open-iscsi transports.
Add support for open-iscsi transports.

This enables use of software or hardware transports viz. be2iscsi,
bnx2i, cxgb3i, cxgb4i, qla4xx, iser and ocs. The default transport
(tcp) happens to be called "default".

Use of non-default transports changes the disk path to the following format:
/dev/disk/by-path/pci-<pci_id>-ip-<portal>-iscsi-<iqn>-lun-<lun_id>

kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples