the fix for 'columns' table only
Rights check for 'routines' table is already done
(see WL2131 Access control for SHOW ... PROCEDURE|FUNCTION ...)
rename 'testtets' database to 'mysqltest' to keep number of
DBs which created by mysql-test as small as possible
mysql-test/r/information_schema.result:
Fix for bug#7214: information_schema: unauthorized user can see metadata
mysql-test/t/information_schema.test:
Fix for bug#7214: information_schema: unauthorized user can see metadata
sql/sql_show.cc:
Fix for bug#7214: information_schema: unauthorized user can see metadata