[Openstack] Make it possible to define image using uuid

[huxcrux]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/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:
Currently the only way to define an image is by using name. The problem when doing this is that all images needs to be set to public in openstack alternativly you need to upload the image to your tennant.

When specifying an image by uuid it can be moved to comunity (meaning not visible in horizons create server tutorial) witout having your servers recreted when re running terraform.

This PR also makes it possible to define another image to be used on masters. If no image is defined the one defined for nodes will be used.

Which issue(s) this PR fixes:

Fixes N/A

Special notes for your reviewer:
This PR does not change the standard behavior just adding the possiblity to select image by uuid and add a separate image on master nodes.

Does this PR introduce a user-facing change?:

Allow to specify openstack images by uuid and have a separate image on master nodes.

[k8s-ci-robot]

Hi @bl0m1. 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.

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[floryut]

/ok-to-test

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[holmsten]

/lgtm