Fixed check for withMacLearning config param in volthaDeploy

Change-Id: I5b90ccf5a121f329500824066ea64f900ad0c482
diff --git a/vars/volthaStackDeploy.groovy b/vars/volthaStackDeploy.groovy
index 37a00d2..bea044b 100644
--- a/vars/volthaStackDeploy.groovy
+++ b/vars/volthaStackDeploy.groovy
@@ -8,6 +8,7 @@
       stackName: "voltha",
       stackId: 1, // NOTE this is used to differentiate between BBSims across multiple stacks
       workflow: "att",
+      withMacLearning: false,
       extraHelmFlags: "",
       localCharts: false,
       onosReplica: 1,