[Openstack] Make sure router port is created before attaching floating IPs

[huxcrux]

What type of PR is this?

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/kind api-change

/kind bug

/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:
This Pr checks that the router and subnet is connected before attempting to attach floating IP's on instances. This can be a problem if the openstack provider have high load on their neutron server.

Which issue(s) this PR fixes:

Fixes N/A

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[k8s-ci-robot]

Hi @bl0m1. Thanks for your PR.

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[huxcrux]

/assign @Miouge1

[holmsten]

/ok-to-test
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bl0m1, holmsten

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[Miouge1]

/lgtm