SONAR suggestion - Synchronize initialization of static fields

Change-Id: I2ddf8220bda49f235ddfc5713174c11a147df354
diff --git a/drivers/utilities/src/main/java/org/onosproject/drivers/utilities/YangXmlUtils.java b/drivers/utilities/src/main/java/org/onosproject/drivers/utilities/YangXmlUtils.java
index bb4dfa5..08ef181 100644
--- a/drivers/utilities/src/main/java/org/onosproject/drivers/utilities/YangXmlUtils.java
+++ b/drivers/utilities/src/main/java/org/onosproject/drivers/utilities/YangXmlUtils.java
@@ -195,7 +195,7 @@
      *
      * @return instance of YangXmlUtils
      */
-    public static YangXmlUtils getInstance() {
+    public static synchronized YangXmlUtils getInstance() {
         if (instance == null) {
             instance = new YangXmlUtils();
         }