Description of problem:

Cloud computing may give users the illusion of infinite capacity, but it is
not always like that. Often quotas are used ensure each project only makes
use their fair share of the cloud's resources.

However, these "reservations" often cause a reduction in cloud utilization.
Ideally you want a way for users who have maxed out their regular resource
quota to be able to opt in to running servers on the spare capacity created
by unused reservations, on the understanding that the server is terminated
if the reservation owner requests their capacity. The user opts into this by
creating a server that is flagged as preemptable.


Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
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Actual results:
no preemption is currently possible and therefore cloud utilization
is reduced as unused capacity that belongs to a different projects
cannot be used by other projects.

Expected results:
when a cloud reaches capasity if a non preemitable instnace is requested
prememeitable instaces are deleted to make room.

if a project reaches its quota it may contiue to launch preemitable instances.
as long as there is capastity to do so.

Additional info: