feat(docs/openstack.md): Put Additional step needed when using calico or kube-router in own section (#9320)

Signed-off-by: Cedric Hnyda <cedric.hnyda@itera.io>

Signed-off-by: Mikael Johansson <mik.json@gmail.com>

* use external_openstack_lbaas_use_octavia for template openstack-cloud-config

* Delete external_openstack_lbaas_use_octavia from default values. Added description and default values of variables to docs

* markdown fix

* make this simple

* set external_openstack_lbaas_use_octavia in default values

* duplicated variable in doc

Add additional metadata configuration options to external Openstack CCM (kubernetes-sigs#6338) (#6339)

* Add additional metadata configuration option to external Openstack CCM (kubernetes-sigs#6338)

* Set the variable external_openstack_metadata_search_order undefined by default

Now the in-tree cloud provider is deprecated and it is recommended to
the external cloud provider for OpenStack instead.
The doc described how to upgrade from the in-tree cloud provider, but
it is better to describe how to deploy the external cloud provider from
scratch instead for current situation.
This updates the OpenStack doc for this usecase.

* Add additional network configuration options to external Openstack CCM (#6083)

* Change the default version of external openstack cloud controller image to v1.18.1 since there was an issue in v1.18.0 where some IPs of the private network were ignored

* Change Network section in external-openstack-cloud-config.j2 to Networking

* Add networking customization information in the openstack documentation

* add documentation for how to upgrade to the new external cloud provider

* add migrate_openstack_provider playbook

* fix codeblock syntax highligth

* make docs for migrating cloud provider better

* update grammar

* fix typo

* Make sure the code is correct markdown

* remove Fenced code blocks

* fix markdown syntax

* remove extra lines and fix trailing spaces

* [jjo] add kube-router support

Fixes cloudnativelabs/kube-router#147.

* add kube-router as another network_plugin choice
* support most used kube-router flags via
  `kube_router_foo` vars as other plugins
* implement replacing kube-proxy (--run-service-proxy=true) via
  `kube_proxy_mode: none`, verified in a _non kubeadm_enabled_
  install, should also work for recent kubeadm releases via
  `skipKubeProxyInstall: true` config

* [jjo] address PR#3339 review from @woopstar

* add busybox image used by kube-router to downloads

* fix busybox download groups key

* rework kubeadm_enabled + kube_router_run_service_proxy

- verify it working ok w/the kubeadm_enabled and
  kube_router_run_service_proxy true or false

- introduce `kube_proxy_remove` fact, to decouple logic
  from kube_proxy_mode (which affects kubeadm configmap
  settings, thus no-good to ab-use it to 'none')

* improve kube-router.md re: kubeadm_enabled and kube_router_run_service_proxy

* address @woopstar latest review

* add inventory/sample/group_vars/k8s-cluster/k8s-net-kube-router.yml

* fix kube_router_run_service_proxy conditional for kube-proxy removal

* fix kube_proxy_remove fact (w/ |bool), add some needed kube-proxy tags on my and existing changes

* update kube-router tolerations for 1.12 compatibility

* add PriorityClass to kube-router DaemonSet

* fix openstack cli syntax

* 'allowed-address' is also a dash, not an underscore

* multiple allowed-address

multiple allowed-address must be in separate parameters

Neutron cli is deprecated - replaced neutron cli commands with equivalent openstack cli commands.

Linked to the issue https://github.com/kubernetes-incubator/kubespray/issues/1359