[VOL-3780] Correctly overriding voltha-onos image

Change-Id: I8e6ecd4a0c38fb36f7f518e59765567ac7e49cce
diff --git a/vars/getVolthaImageFlags.groovy b/vars/getVolthaImageFlags.groovy
index 76dda9d..8770ff2 100644
--- a/vars/getVolthaImageFlags.groovy
+++ b/vars/getVolthaImageFlags.groovy
@@ -29,6 +29,8 @@
       // BBSIM has a different format that voltha, return directly
       return "--set images.bbsim.tag=${tag},images.bbsim.pullPolicy=${pullPolicy},images.bbsim.registry='' "
     break
+    case "voltha-onos":
+      return "--set onos-classic.image.repository=voltha/voltha-onos,onos-classic.image.tag=citest,onos-classic.image.pullPolicy=${pullPolicy}"
     default:
       return ""
     break