If we're updating existing allocations for an instance due
to the project_id/user_id not matching the instance, we should
use the consumer_generation parameter, new in placement 1.28,
to ensure we don't overwrite the allocations while another
process is updating them.
As a result, the include_project_user kwarg to method
get_allocations_for_consumer is removed since nothing else
is using it now, and the minimum required version of placement
checked by nova-status is updated to 1.28.
Change-Id: I4d5f26061594fa9863c1110e6152069e44168cc3
Matt Riedemann
660e328a25