For non-XOS charts, use a global registry var, split docker image name/tag/pullPolicy

Change-Id: Icffc569e2c152e0b413f4c7b7d9a546bd9a3ef58
diff --git a/dhcp-server/values.yaml b/dhcp-server/values.yaml
index b0c8bb9..7ac1ba7 100644
--- a/dhcp-server/values.yaml
+++ b/dhcp-server/values.yaml
@@ -1,3 +1,4 @@
+---
 # Copyright 2017-present Open Networking Foundation
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -14,13 +15,18 @@
 
 # helm install dhcp-server -n dhcp-server
 
-dhcpServerImage: 'networkboot/dhcpd:latest'
-imagePullPolicy: Always
+image:
+  repository: 'networkboot/dhcpd'
+  tag: '{{ .Chart.AppVersion }}'
+  pullPolicy: 'Always'
+
+global:
+  registry: ''
 
 config: |
 
   subnet 10.233.0.0 netmask 255.255.0.0 {
-    range 10.233.0.1 10.233.0.2; 
+    range 10.233.0.1 10.233.0.2;
   }
   subnet 10.200.0.0 netmask 255.255.0.0 {
     range 10.200.0.1 10.200.0.253;