Add constants for extended attribute groups
Add constants for extended attribute groups

Extended attribute groups can be provided per the 'xag' variable on the
read operation within the adapter.  They are mostly used for the Virtual
I/O Server.  They provide reads for specific attributes, and can greatly
reduce the overall read time of the element.

This change set puts a set of the common attribute groups in the Virtual
I/O Server wrapper.

Change-Id: I38d450313c8be6bd8f32967ed2f08529d0e0ddc0

pypowervm/pypowervm,powervm/pypowervm