placement: Use the less generic PlacementApi service name
placement: Use the less generic PlacementApi service name

I5dbce7883f86ba6a92f48a398b0d0eb9b743d212 had incorrectly set this to
Placement instead of PlacementApi.

Change-Id: I5b233913ffd4e88ebd82332a55ae3044e505fc15

openstack/tripleo-common,openstack/tripleo-common