Add batch-mode flag when running maven

Change-Id: I91489f7615d22989ef06874f7559100ccb4379fe
diff --git a/jjb/onos/onos-yang-tools-verify.sh b/jjb/onos/onos-yang-tools-verify.sh
index 5c11c16..e406f68 100755
--- a/jjb/onos/onos-yang-tools-verify.sh
+++ b/jjb/onos/onos-yang-tools-verify.sh
@@ -3,4 +3,4 @@
 # exit on errors
 set -eu -o pipefail
 
-mvn clean install
+mvn -B clean install