https://review.openstack.org/#/c/290534/ was reverted as it did not
work in the case where the node running the scheduler is also a
compute node.
As cpu_allocation_ratio, ram_allocation_ratio and
disk_allocation_ratio can all be set on the scheduler node and/or
overridden on the compute node level, it makes sense to move these
parameters to the top level.
Change-Id: I26e9fd5517ebdde76db0a2d7f38dde4883c599bc