Refactor huawei Dorado array iSCSI driver

This is the second patch, changes as follows:
1.Add ISCSIDriver for Dorado arrays. The ISCSIDriver inherit from T.
1.Add a common class DoradoCommon for both FC and iSCSI drivers. The common class
inherit from T common for they have many common functions.
2.Add unit test for Dorado drivers.

Change-Id: I7ff2cc1e0d058b7a3d9e55644769ec74075f962f
Merge "Refactor huawei Dorado array iSCSI driver"