Fixed log warning for failed persistence. It was not logging the exception in the correct slot and was using the name of the unit in the message rather than in brackets.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5518 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/util/PersistingUnit.java

@@ -71,7 +71,7 @@ public abstract class PersistingUnit extends Invoker.Unit
         if (error instanceof InvocationException) {
             _listener.requestFailed(error.getMessage());
         } else {
-            log.warning(getFailureMessage(), error);
+            log.warning("Unit threw an exception", "message", getFailureMessage(), error);
             _listener.requestFailed(InvocationCodes.INTERNAL_ERROR);
         }
     }