Ignore 'complete' messages from suppressed workers
Ignore 'complete' messages from suppressed workers

If we have a database where one copy of a partition contributes zero
rows to a reduce view but another copy of the same partition contributes
one or more rows we can end up erroneously removing a worker which has
already contributed a row to a response.  This puts the coordinator into
an inconsistent state and can ultimately cause the response to hang.

The fix is simple -- just guard processing of 'complete' messages by
checking if the worker sending the message has already lost the race to
another copy.

BugzID: 13461

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb