Swapping defaults for globals due to helm chart changes

Change-Id: I93fdeb7d7dec871d046764ad30f6a2d5809b1fd4
diff --git a/values.yaml b/values.yaml
index d864f2a..f27efc3 100644
--- a/values.yaml
+++ b/values.yaml
@@ -21,6 +21,10 @@
 # set "<VALUE>" to "master". Similarly, if you want to use the images
 # generated from the HEAD of the "voltha-2.1" git branches, then uncomment
 # this block and replace "<VALUE>" with "voltha-2.1".
+global:
+  image_tag: master
+  image_pullPolicy: Always
+# defaults is maintained for backward compatibility
 defaults:
   image_tag: master
   image_pullPolicy: Always