Add support to use exisitng fips with terraform openstack

[anders-elastisys]

What type of PR is this?
/kind feature

What this PR does / why we need it:

This PR adds Terraform Openstack support for specifying existing floating IPs on each machine listed in k8s_nodes and k8s_masters with a new optional variable reserved_floating_ip which is only used when the floating_ip variable is set to true. If reserved_floating_ip is not set and floating_ip is true, a new floating IP will be created same as before.

When reserved_floating_ip is set, that IP will get released and not deleted when deleting all Terraform resources.

Known limitations:

• If you specify the same IP for reserved_floating_ip on multiple hosts, Terraform will not complain and only one machine gets assigned the IP in the end, as there is currently no check for whether or not the specific IP has already been assigned. The output will show the same IP several times as well.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[k8s-ci-robot]

Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: anders-elastisys
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[k8s-ci-robot]

Hi @anders-elastisys. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[yankay]

/ok-to-test