log exception backtrace on RESTCONF error

Change-Id: I57cc61756012cf79244c577e1e786ac467570319
diff --git a/apps/restconf/utils/src/main/java/org/onosproject/restconf/utils/RestconfUtils.java b/apps/restconf/utils/src/main/java/org/onosproject/restconf/utils/RestconfUtils.java
index 41fcf39..4cd004a 100644
--- a/apps/restconf/utils/src/main/java/org/onosproject/restconf/utils/RestconfUtils.java
+++ b/apps/restconf/utils/src/main/java/org/onosproject/restconf/utils/RestconfUtils.java
@@ -145,7 +145,8 @@
         } catch (RestconfException ex) {
             throw ex;
         } catch (Exception ex) {
-            log.error("convertJsonToDataNode failure: {}", ex.getMessage());
+            log.error("convertJsonToDataNode failure: {}", ex.getMessage(), ex);
+            log.info("Failed JSON: \n{}", rootNode);
             log.debug("convertJsonToDataNode failure", ex);
             throw new RestconfException("ERROR: JSON cannot be converted to DataNode",
                     ex, RestconfError.ErrorTag.OPERATION_FAILED, INTERNAL_SERVER_ERROR,