Those settings in devstack were introduced by [1] and it seems to be
working fine so far.
Lets try to use it in the Neutron scenario, functional and fullstack
jobs to save some memory.
[1] https://review.opendev.org/c/openstack/devstack/+/873646
Change-Id: Idb1422acc7d23c6d8f9777ec5ebd9b040c99717a