MountListener: Improve error logging

Signed-off-by: San Mehat <san@google.com>
diff --git a/services/java/com/android/server/MountListener.java b/services/java/com/android/server/MountListener.java
index 5a1107b..5eea335 100644
--- a/services/java/com/android/server/MountListener.java
+++ b/services/java/com/android/server/MountListener.java
@@ -123,8 +123,8 @@
                                 try {
                                     handleUnsolicitedEvent(code, event, tokens);
                                 } catch (Exception ex) {
-                                    Log.e(TAG, "Error handling unsolicited event '" + event + "'");
-                                    Log.e(TAG, ex.toString());
+                                    Log.e(TAG, String.format(
+                                            "Error handling '%s'", event), ex);
                                 }
                             } else {
                                 try {