Clean up IronicNodeStates.update_from_compute_node

This method was needlessly wordy.

This patch does not change any functionality, merely makes the method
easier to read.

Change-Id: I7d66ea5e2146877f70a2e9060d3d4244f9493b9d
Improved coverage for ironic API

Added missing tests for get_one() in ironic.tests.api.*

Change-Id: I3d65441f4bf3857f40e856f692858e9b3ac19568
Merge "Improved coverage for ironic API"
Merge "Clean up IronicNodeStates.update_from_compute_node"