Standardize the release-status of unknown / rolling distros

@pinotree raised that the current status is:

• asianux-unknown: prerelease
• caasp-unknown: no release-status (= released)
• debian-testing: no release-status (= released)
• fedora-rawhide: prerelease
• fedora-unknown: prerelease
• nixos-unknown: no release-status (= released)
• nixos-unstable: no release-status (= released)
• opensuse-factory: snapshot
• opensuse-tumbleweed: no release-status (= released)
• rhel*unknown: no release-status (= released)
• scientificlinux-7-unknown: no release-status (= released)
• sle*unknown: no release-status (= released)

From those:

• debian-testing, opensuse-tumbleweed, nixon-unstable, fedora-rawhide, silverblue-rawhide (in the process of being reviewed), IMHO, could be considered "rolling";
• For all the unknowns, I'd go for either released, but I don't have any strong preference/

Opinions?