Comment 7 for bug 1536663

When read-free-replication is enabled for tokudb and there is no
explicit pk for replicated table there can be dublicated records in the table
on update operation.

Consider this update operation:
UPDATE t SET a = a + 10 WHERE b = 'b';
The master does rows lookup and updates the rows which values
correspond to the condition. The update events are written to binary log with
rows values from the master. As rows lookup is forbidden for slave
the new rows are added instead of updating corresponding rows.

Without the fix there will be several rows with b = 'b' in the table
on slave instead of one updated row.

The fix disables RFR for tables without explicit pk and do rows lookup
for update and delete binlog events and issues warning.