Packer incompatible with Fedora 33 or Fedora 34

[jsf9k]

🐛 Summary

Fedora 33 updated the system-wide crypto policy to disallow SHA-1 hashes in signatures. This is a good thing, especially since OpenSSH follows suit as of version 8.8.

Unfortunately, Packer cannot support this change because of an inflexibility in go (see also golang/go#36261 and golang/go#37278). This is blocking us from upgrading our FreeIPA AMI to Fedora 33+, since Packer is unable to ssh to the instance launched from the base AMI after it is spun up.

It should be possible for us to workaround this limitation by switching to a different system-wide crypto policy via the userdata fed to the base AMI when it is spun up. This change can then be undone via an additional of a Packer provisioner in the packer.json configuration file.