When there are errors we still need to update flow control freed bytes

If an upr message cannot be processed due to an error we still need
to account for it as freed bytes.

Change-Id: I394b77b35dce1013618f83bcc6a02bb8fb4c7af1
Reviewed-on: http://review.couchbase.org/37918
Tested-by: Michael Wiederhold <mike@couchbase.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>