add support for voltha classic helm chart

Change-Id: I1a0a5ac4fe95873276c3cca3faeb98713667e075
diff --git a/releases/voltha-2.3 b/releases/voltha-2.3
index 9904f23..e60061b 100644
--- a/releases/voltha-2.3
+++ b/releases/voltha-2.3
@@ -8,6 +8,7 @@
 export VOLTHA_ADAPTER_OPEN_OLT_CHART_VERSION=2.3.2
 export VOLTHA_ADAPTER_OPEN_ONU_CHART_VERSION=2.3.0
 export ONOS_CHART_VERSION=3.0.1
+export WITH_ONOS=legacy
 
 # defaults.image_tag=null will use the image tags in the Helm charts rather than
 # kind-voltha's default which is 'master'.