Support rpm platforms without yum

[h0tw1r3]

observed the latest rockylinux 9 containers do not have a yum symlink to dnf anymore.

Related:

• https://github.com/puppetlabs/provision/pull/261
• https://github.com/puppetlabs/litmusimage/pull/88

[h0tw1r3]

Should the default remain yum in the case both are present?

No, technically yum has been deprecated since EL8. Anytime it's present it should be preferred.