The nova_cell_v2_discover_hosts.py was moved to run on compute
nodes instead of controllers to allow adding computes without
touching controllers and in case multiple stacks are used to
manage compute nodes. In case the nova-manage command, run by
nova_cell_v2_discover_hosts.py, gets triggered at the same time
on compute nodes races.
With this change if this is _not_ an additional cell:
* in docker_config step4, on every compute, we start the nova-compute
container and then start a (detach=false) container to wait for
it's service to appear in the service list.
* in docker_config step5, on the bootstrap node only, we run the
discovery.
Change-Id: I1a159a7c2ac286373df2b7c566426b37b7734961
Closes-bug: 1824445
Co-authored-by: mschuppert@redhat.com
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