Fix xos-service-upgrade job jailing because of missing cord repo

Required after replacing file-based URLs with
https://charts.opencord.org in the cord charts requirements.

Change-Id: I1e649d17880a8456b1ef9deceea7fff5545394d5
diff --git a/jjb/pipeline/xos-service-upgrade.groovy b/jjb/pipeline/xos-service-upgrade.groovy
index 173c463..6ddd7ef 100644
--- a/jjb/pipeline/xos-service-upgrade.groovy
+++ b/jjb/pipeline/xos-service-upgrade.groovy
@@ -86,6 +86,7 @@
            helm init
            sleep 60
            helm repo add incubator https://kubernetes-charts-incubator.storage.googleapis.com/
+           helm repo add cord https://charts.opencord.org
            '''
       }
     }