RedHat 9 based appliances - add option "-cpu host"

[b-ehlers]

Fixed issue #818, add option "-cpu host" to RedHat 9 based appliances.

Replaced the Stream-9 image of the centos-cloud appliance to an image, that is available, updated the usage instruction.

@Da-Geek - While it's nice, that you update appliances, please check that your updates are working.

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Before submitting a pull request, please check the following.

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When updating an existing appliance:

• [x] The new version is on top.
• [x] The filenames in the "images" section are unique, to avoid appliances / version overwriting each other.

• [x] If you forked the repo, running check.py doesn't drop any errors for the updated file.