add optional parameter extra_groups for k8s_nodes in openstack terraform

[rptaylor]

What type of PR is this?

/kind feature

What this PR does / why we need it:
Expand the ad-hoc k8s_nodes definitions with an optional parameter that allows specifying additional Ansible group memberships for specific nodes.
This can be used to e.g. create special nodes for calico route reflector in the calico_rr group.

Special notes for your reviewer:

Does this PR introduce a user-facing change?:
No. Default behaviour remains unchanged. However users may wish to know:

Add an optional extra_groups parameter for k8s_nodes (e.g. to configure calico route reflector nodes on Openstack using the calico_rr group)

[k8s-ci-robot]

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[rptaylor]

My tests show that it works. By default there is no change. Here is the output from terraform plan when I defined extra_groups:

 # module.compute.openstack_compute_instance_v2.k8s_nodes["a-3"] will be updated in-place
  ~ resource "openstack_compute_instance_v2" "k8s_nodes" {
        id                  = "219c702c-30d8-4ba0-919c-bf28025ef68b"
      ~ metadata            = {
          ~ "kubespray_groups" = "kube_node,k8s_cluster,no_floating," -> "kube_node,k8s_cluster,no_floating,TEST1,TEST2"
            # (3 unchanged elements hidden)
        }
        name                = "cluster-dev-k8s-node-a-3"
        tags                = []
        # (14 unchanged attributes hidden)

        # (1 unchanged block hidden)
    }

[rptaylor]

@holmsten @liupeng0518 could you please take a look?
Thanks.

[cristicalin]

Hi @rptaylor , please rebase this PR on latest state of the master branch to be able to pass the CI tests.

[rptaylor]

@cristicalin I rebased and the tests are passing.

[oomichi]

/ok-to-test
/lgtm

[rptaylor]

/assign @holmsten
can this be merged now?
@cristicalin

[floryut]

@rptaylor All good, sorry for the lag 👍

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: floryut, rptaylor

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