Fix SeaMicro driver post landing for ba207b4aa0

This patch is a post landing for ba207b4aa086da32df891b8627515acc93830da8

Fixing:
* Remove vim config line
* Update DocStrings to include the exceptions the methods might raise
* Remove None as default value for dict get()
* Raises the right exception (InvalidParameterValue) if set_power_state
  is called with invalid power state.

Change-Id: Ie4c00a25050b5f4010b3c8da0c57fcdb7fe70253
Merge "Fix SeaMicro driver post landing for ba207b4aa0"