Fixes #37835 - Add user and netapi to Salt config

* Set user for running Salt Master service due to 3006 changes
  https://docs.saltproject.io/en/3006/topics/releases/3006.0.html#linux-packaging-salt-master-salt-user-and-group

* Add netapi_enable_clients explicitly due to 3006 changes
  https://docs.saltproject.io/en/master/topics/netapi/netapi-enable-clients.html#select-client-interfaces-to-enable

templates/plugin/salt_master.conf.erb

@@ -15,6 +15,11 @@ autosign_file: <%= scope.lookupvar('foreman_proxy::plugin::salt::autosign_file')
 # permissive_pki_access: True
 
 
+##
+# Salt Master service user
+user: <%= scope.lookupvar('::foreman_proxy::plugin::salt::user') %>
+
+
 ##
 # Node classifier
 master_tops:
@@ -39,6 +44,10 @@ rest_cherrypy:
   ssl_key: <%= @foreman_ssl_key %>
   ssl_crt: <%= @foreman_ssl_cert %>
 
+netapi_enable_clients:
+  - local
+  - local_async
+
 
 ##
 # Remote execution provider