PCBC-251: Add missing prefix for incr/decr/unlock

Change-Id: I350d2492f5a5eb196d1474650be138a842348920
Reviewed-on: http://review.couchbase.org/29246
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>