Only setup *_PROXY env variables where needed (#7095)

no_proxy is a pain to get right, and having proxy variables present causes issues
(k8s components get proxy configuration after upgrade, see #7100)

It's better to only configure what require proxy:
- the runtime (containerd/docker/crio)
- the package manager + apt_key
- the download tasks

Tested with the following clusters
- 4 CentOS 8 nodes
- 1 Ubuntu 20.04 node

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

roles/bootstrap-os/tasks/main.yml

@@ -5,7 +5,6 @@
   changed_when: false
   # This command should always run, even in check mode
   check_mode: false
-  environment: {}
 
 - include_tasks: bootstrap-centos.yml
   when: '"CentOS" in os_release.stdout or "Oracle" in os_release.stdout'