salt: set 1 env var per line in containerd unit

For the sake of clarity, we set 1 env variable
per line, instead of all the variables on a single
`Environment` entry in the containerd unit file

Refs: #2052

salt/metalk8s/container-engine/containerd/files/50-metalk8s.conf.j2

@@ -2,4 +2,6 @@
 # See https://github.com/containerd/containerd/issues/3201
 # See https://github.com/containerd/containerd/pull/3202
 LimitNOFILE=1048576
-Environment="{{ environment }}"
+{%- for key, value in (environment | default({}, True)).items() %}
+Environment={{ key }}={{ value }}
+{%- endfor %}

salt/metalk8s/container-engine/containerd/installed.sls

@@ -48,18 +48,18 @@ Create containerd service drop-in:
     - makedirs: true
     - dir_mode: 0755
     - context:
-      environment: >-
+      environment:
       {%- if proxies %}
         {%- set no_proxy = ["localhost", "127.0.0.1"] + networks.values() %}
         {%- if proxies.no_proxy | default %}
           {%- do no_proxy.extend(proxies.no_proxy) %}
         {%- endif %}
-        NO_PROXY={{ no_proxy | unique | join(",") }}
+        NO_PROXY: "{{ no_proxy | unique | join(",") }}"
         {%- if proxies.http | default %}
-        HTTP_PROXY={{ proxies.http }}
+        HTTP_PROXY: "{{ proxies.http }}"
         {%- endif %}
         {%- if proxies.https | default %}
-        HTTPS_PROXY={{ proxies.https }}
+        HTTPS_PROXY: "{{ proxies.https }}"
         {%- endif %}
       {%- endif %}