corrupts a MERGE table

Post-pushbuild fix for a Valgrind warning.


mysql-test/r/merge.result:
  Bug#26379 - Combination of FLUSH TABLE and REPAIR TABLE
              corrupts a MERGE table
  Fixed test result.
mysql-test/t/merge.test:
  Bug#26379 - Combination of FLUSH TABLE and REPAIR TABLE
              corrupts a MERGE table
  Removed unnecessary statements from test.
sql/sql_trigger.cc:
  Bug#26379 - Combination of FLUSH TABLE and REPAIR TABLE
              corrupts a MERGE table
  Fixed usage of db and table_name for
  close_data_files_and_morph_locks().