[cloud-init] (8 commits) ...Switch to dnf instead of yum when available

[gholms]

Summary of changes:

  daa1660... Stop depending on git to build (*)
  22dbc1a... Stop implicitly listing doc files twice (*)
  0a23a4d... Add recognition of 3 ecdsa-sha2-nistp* ssh key types (*)
  a510c9b... Fix handling of user group lists that contain spaces (*)
  851688f... Change network.target systemd deps to network-online.target (*)
  c33ce8c... Ensure cloud-init.service doesn't write all over the login  (*)
  469555b... Stop enabling services in %post (*)
  37c3202... Switch to dnf instead of yum when available (*)

(*) This commit already existed in another branch; no separate mail sent