Adds extended status fields to nova list

The nova list command now includes 'Task State' and 'Power State' fields to
bring parity with the dashboard.

	* Add helper function _translate_extended_states()
	to convert extended states to human

Fixes: bug #954750

Change-Id: I564b7f88e9e2524d8e4ffe21a51608c5e3b23d2d
Merge "Adds extended status fields to nova list"