Huawei: Refactor driver for the second time

Huawei: Refactor driver for the second time

After a few new features being added into drivers,
we found it hard to maintain the code. For further working,
we need to refactor our code. The work contains the following:
1. Define a new class, named HuaweiConf, to parse xml config file.
   We used an external xml file to store SAN info.
   But we do config parsing anywhere in our code,
   even two different functions do the same parsing.
2. Adjust some function structures.
3. Rename some functions & variables.

DocImpact
Implements: blueprint refactor-huawei-driver
Change-Id: If935a38399809cf95848825344fb837bf04a7dd3