Killing the insert-select statement corrupts the MyISAM table only
when the destination table is empty and when it has indexes. When 
we bulk insert huge data and if the destination table is empty we 
disable the indexes for fast inserts, data is then inserted and 
indexes are re-enabled after bulk_insert operation
                        
Killing the query, aborts the repair table operation during enable
indexes phase leading to table corruption.
                      
We now truncate the table when we detect that enable indexes is
killed for bulk insert query.As we have an empty table before the 
operation, we can fix by truncating the table.

mysql-test/r/myisam.result:
  Result file for BUG#40827
mysql-test/t/myisam.test:
  Testcase for BUG#40827
storage/myisam/ha_myisam.cc:
  Fixed end_bulk_insert() method to truncate the table when we detect enable 
  index operation is killed.