Add fetching of network config data
Add fetching of network config data

This is compatible with the ipmi model for now, and raising exceptions
in multi-interface environments.  Future will have helper to list and
use interface as parameter.

Change-Id: I648edc1546a12dbd7f3ca9548ce6db3dfadd4827

openstack/pyghmi,stackforge/pyghmi,openstack/pyghmi