MB-100: fix in logs for VBucketAwareMemcached

Change-Id: Ia556be751cfdd47b5aec785d61b6bd458da1f45a
Reviewed-on: http://review.couchbase.org/24665
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>