MB-100 Fix log message.

Change-Id: I3a36f58af95d76b37fa5c247a33672d05d1f6516
Reviewed-on: http://review.couchbase.org/28162
Reviewed-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Junyi Xie <junyi.couchbase@gmail.com>
Tested-by: Junyi Xie <junyi.couchbase@gmail.com>