Salt: support systemd (don't assume Redhat <=> systemd)

Also work around problems with Salt & systemd services, in particular
that Salt doesn't issue a daemon-reload.

cluster/saltbase/salt/salt-helpers/init.sls

@@ -0,0 +1,15 @@
+{% if pillar.get('is_systemd') %}
+/opt/kubernetes/helpers:
+  file.directory:
+    - user: root
+    - group: root
+    - makedirs: True
+    - dir_mode: 755
+
+/opt/kubernetes/helpers/services:
+  file.managed:
+    - source: salt://salt-helpers/services
+    - user: root
+    - group: root
+    - mode: 755
+{% endif %}