Ensure kubeadm doesn't use proxy (#7275)

* Move proxy_env to kubespray-defaults/defaults

There is no reasons to use set_facts here

Signed-off-by: Etienne Champetier <e.champetier@ateme.com>

* Ensure kubeadm doesn't use proxy

*_proxy variables might be present in the environment (/etc/environment, bash profile, ...)
When this is the case we end up with those proxy configuration in /etc/kubernetes/manifests/kube-*.yaml manifests

We cannot unset env variables, but kubeadm is nice enough to ignore empty vars
93d288e2a4/cmd/kubeadm/app/util/env.go (L27)

Signed-off-by: Etienne Champetier <e.champetier@ateme.com>

scale.yml

@@ -69,6 +69,7 @@
         --config {{ kube_config_dir }}/kubeadm-config.yaml
         upload-certs
         --upload-certs
+      environment: "{{ proxy_disable_env }}"
       register: kubeadm_upload_cert
       changed_when: false
     - name: set fact 'kubeadm_certificate_key' for later use