Fixed check for withMacLearning config param in volthaDeploy

Change-Id: I5b90ccf5a121f329500824066ea64f900ad0c482
diff --git a/jjb/pipeline/voltha/master/bbsim-tests.groovy b/jjb/pipeline/voltha/master/bbsim-tests.groovy
index a164d55..fefa4d4 100755
--- a/jjb/pipeline/voltha/master/bbsim-tests.groovy
+++ b/jjb/pipeline/voltha/master/bbsim-tests.groovy
@@ -73,7 +73,7 @@
             infraNamespace: infraNamespace,
             volthaNamespace: volthaNamespace,
             workflow: workflow.toLowerCase(),
-            withMacLearning: enableMacLearning,
+            withMacLearning: enableMacLearning.toBoolean(),
             extraHelmFlags: localHelmFlags,
             localCharts: localCharts,
             bbsimReplica: olts.toInteger(),