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>

cluster.yml

@@ -2,21 +2,6 @@
 - name: Check ansible version
   import_playbook: ansible_version.yml
 
-- hosts: all
-  gather_facts: false
-  tags: always
-  tasks:
-    - name: "Set up proxy environment"
-      set_fact:
-        proxy_env:
-          http_proxy: "{{ http_proxy | default ('') }}"
-          HTTP_PROXY: "{{ http_proxy | default ('') }}"
-          https_proxy: "{{ https_proxy | default ('') }}"
-          HTTPS_PROXY: "{{ https_proxy | default ('') }}"
-          no_proxy: "{{ no_proxy | default ('') }}"
-          NO_PROXY: "{{ no_proxy | default ('') }}"
-      no_log: true
-
 - hosts: bastion[0]
   gather_facts: False
   roles:
@@ -43,7 +28,6 @@
     - { role: kubernetes/preinstall, tags: preinstall }
     - { role: "container-engine", tags: "container-engine", when: deploy_container_engine|default(true) }
     - { role: download, tags: download, when: "not skip_downloads" }
-  environment: "{{ proxy_env }}"
 
 - hosts: etcd
   gather_facts: False
@@ -75,7 +59,6 @@
   roles:
     - { role: kubespray-defaults }
     - { role: kubernetes/node, tags: node }
-  environment: "{{ proxy_env }}"
 
 - hosts: kube-master
   gather_facts: False
@@ -127,7 +110,6 @@
   roles:
     - { role: kubespray-defaults }
     - { role: kubernetes-apps, tags: apps }
-  environment: "{{ proxy_env }}"
 
 - hosts: k8s-cluster
   gather_facts: False