locking type of temp table

The problem is that INSERT INTO .. SELECT FROM .. and CREATE
TABLE .. SELECT FROM a temporary table could inadvertently
overwrite the locking type of the temporary table. The lock
type of temporary tables should be a write lock by default.

The solution is to reset the lock type of temporary tables
back to its default value after they are used in a statement.

mysql-test/r/innodb_mysql.result:
  Add test case result for Bug#41348
mysql-test/r/temp_table.result:
  Add test case result for Bug#41348
mysql-test/t/innodb_mysql.test:
  Add test case for Bug#41348
mysql-test/t/temp_table.test:
  Add test case for Bug#41348
sql/sql_base.cc:
  Allow the lock type of temp tables to be overwritten now that
  the the value is being restored once the table is marked as
  free for re-use. This makes the behavior consistent with that
  of non-temporary tables and avoids confusion.