Add http proxy support for minion

salt/files/minion.d/f_defaults.conf

 {{ get_config('master', 'salt') }}
 {%- endif %}
 
+# Set http proxy information for the minion when doing requests
+{% if 'proxy_host' in cfg_minion -%}
+{%- do default_keys.append('proxy_host') %}
+proxy_host: {{ cfg_minion['proxy_host'] }}
+{% else -%}
+#proxy_host:
+{%- endif %}
+{% if 'proxy_port' in cfg_minion -%}
+{%- do default_keys.append('proxy_port') %}
+proxy_port: {{ cfg_minion['proxy_port'] }}
+{% else -%}
+#proxy_port:
+{%- endif %}
+{% if 'proxy_username' in cfg_minion -%}
+{%- do default_keys.append('proxy_username') %}
+proxy_username: {{ cfg_minion['proxy_username'] }}
+{% else -%}
+#proxy_username:
+{%- endif %}
+{% if 'proxy_password' in cfg_minion -%}
+{%- do default_keys.append('proxy_password') %}
+proxy_password: {{ cfg_minion['proxy_password'] }}
+{% else -%}
+#proxy_password:
+{%- endif %}
+
 # If multiple masters are specified in the 'master' setting, the default behavior
 # is to always try to connect to them in the order they are listed. If random_master is
 # set to True, the order will be randomized instead. This can be helpful in distributing