Printing stacktrace in UiWebSocket.java catch block log message

Change-Id: I867583e9e4881e6264196062f2c13c591c7ca78d
diff --git a/web/gui/src/main/java/org/onosproject/ui/impl/UiWebSocket.java b/web/gui/src/main/java/org/onosproject/ui/impl/UiWebSocket.java
index 4df3edf..b80c11f 100644
--- a/web/gui/src/main/java/org/onosproject/ui/impl/UiWebSocket.java
+++ b/web/gui/src/main/java/org/onosproject/ui/impl/UiWebSocket.java
@@ -109,7 +109,7 @@
             log.info("GUI client connected");
 
         } catch (ServiceNotFoundException e) {
-            log.warn("Unable to open GUI connection; services have been shut-down");
+            log.warn("Unable to open GUI connection; services have been shut-down", e);
             this.connection.close();
             this.connection = null;
             this.control = null;