Support discovery of mutiple devices from centralized management tools

[NajmudheenCT]

Issue/Feature Description:
Currently delfin supports a single device discovery. Most of the vendors provide centralized management tools to manage mutiple devices .

• Analysis and Design Analysis and Design of Delfin Centralized Manager Support architecture-analysis#110
• Implementation

Why this issue to fixed / feature is needed(give scenarios or use cases):
To support mutiple devices discovery from centralized management tools
How to reproduce, in case of a bug:

Other Notes / Environment Information: (Please give the env information, log link or any useful information for this issue)

[NajmudheenCT]

Design document link sodafoundation/architecture-analysis#107