Updating bbsim variable file nomenclature

Change-Id: I21f289c71e5aae6a95fd3d4368997e09d100f0b5
diff --git a/bbsim/values.yaml b/bbsim/values.yaml
index 6ef6634..7cd295b 100644
--- a/bbsim/values.yaml
+++ b/bbsim/values.yaml
@@ -40,10 +40,11 @@
 # -k option
 kafka_broker: 'cord-kafka.default.svc.cluster.local:9092'
 
-image:
-  repository: 'voltha/voltha-bbsim'
-  tag: '{{ .Chart.AppVersion }}'
-  pullPolicy: 'Always'
+images:
+  bbsim:
+    repository: 'voltha/voltha-bbsim'
+    tag: '{{ .Chart.AppVersion }}'
+    pullPolicy: 'Always'
 
 global:
   registry: ''