Update documentation to put kube-ovn-controller pods in a central c…

[awfabian-rs]

…luster location.

JIRA:OSPC-393

[awfabian-rs]

• kube-ovn-controller pods play a critical central role
  • However, Kube-OVN seems to allow them to schedule on any kind of node
    • You can see this by contrasting the nodeSelector on ovn-central Deployment with the kube-ovn-controller Deployment:
      • nodeSelector for ovn-central deployment in kubespray
      • nodeSelector for kube-ovn-controller Deployment in kubespray
    • This seems undesirable for Genestack because it would allow these to run on random compute nodes
• I considered where to change this:
  • kustomize doesn't seem suitable
    • it would need a copy of the Deployment which has many variables with IP addresses, etc. already filled in. It just doesn't seem like it would work.
  • this doesn't seem likely to get merged to upstream kubespray and it would take some time to get through the contribution requirements
• I tried this patch on my test cluster and ran kubespray's cluster.yml and the patch (nodeSelector on the kube-ovn-controller Deployment) stayed in place.

This seems like a logical place to put this and a logical way to centralize these and centralizing these pods seems like a good idea for Genestack, as opposed to allowing them to land on random compute and other types of nodes.

Feel free to merge if this looks good, otherwise, let me know if you have any questions, request changes, etc.

Thanks,

Adam