Set 'enableDhcpIgmpOnProvisioning' flag in VOLTHA ONOS

Change-Id: Ibbc4c8e3d9c9f2d8e345d2fba9524f4908310b47
diff --git a/xos-services/onos-service/templates/_tosca.tpl b/xos-services/onos-service/templates/_tosca.tpl
index d487b7d..c7623f7 100644
--- a/xos-services/onos-service/templates/_tosca.tpl
+++ b/xos-services/onos-service/templates/_tosca.tpl
@@ -186,4 +186,17 @@
         - service_instance:
             node: onos_app#olt
             relationship: tosca.relationships.BelongsToOne
-{{- end -}}
\ No newline at end of file
+
+    olt-config-attr:
+      type: tosca.nodes.ServiceInstanceAttribute
+      properties:
+        name: /onos/v1/configuration/org.opencord.olt.impl.Olt?preset=true
+        value: >
+          {
+            "enableDhcpIgmpOnProvisioning" : true
+          }
+      requirements:
+        - service_instance:
+            node: onos_app#olt
+            relationship: tosca.relationships.BelongsToOne
+{{- end -}}