Fix Huawei drivers to support other host OSs

Fix Huawei drivers to support other host OSs

Huawei drivers create Linux hosts by default when attaching volumes.
This patch makes them also support Windows, XenServer, AIX, etc.
The default OS is still Linux if it is not specified.

Users need to configure the host OS types in Huawei XML configuration
file. They need to set the items like this:
<Host OSType="Windows" HostIP="10.10.0.1, 10.10.0.2, ..." />
<Host .../>

When attaching a volume, the driver will get the host IP from nova. We
compare that IP with the IP in "HostIP" to get the corresponding OS type.

Closes-bug: #1229759
Change-Id: I36fd52b97f790f1c68eaf24b6c12e7ef5d16145d