Add document for Huawei cinder volume driver

Add configuration guide for Huawei cinder volume drive
in computevolumes.xml.

Fixes bug: 1159842

Patchset moves it to the block storage admin guide as a
file in the drivers directory.

Change-Id: Ia1953b7ad78d0428a0cdd16ee3569f379d289d3e
Merge "Add document for Huawei cinder volume driver"