MB-100: fix typo

Change-Id: If4f05881818041703b51a8927b92b4adcde9cf05
Reviewed-on: http://review.couchbase.org/25636
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>