Following on from I5260b4d3478008a76fbe53fdbb716004d11b22df in Stein and
ahead of the removal of the Placement deployment logic from puppet-nova
we can now remove nova_placement from POI. We can also switch the one
remaining job using this class to the puppet-placement based placement
class.
Change-Id: Ia56e403b0f7171ee3583e768404d5f65acd61576