Lots of get failures from couchkvstore in the logs

In a two hour period I saw 4560 instances of the message on one node below which is printed from the couchkvstore multi-get function. We need to decide whether or not this behavior is expected and if it is then we need a way to suppress false positives.

Thu Jul 10 15:34:39.384231 PDT 3: (saslbucket) Warning: failed to fetch data from database, vBucket=963 key=B33BB0AF-62_558753 error=document not found [none]