Code cleanups during code reviews

Ensure we get error if INSERT IGNORE ... SELECT fails
Fixed wrong key_part->key_length usage in index_merge

mysql-test/r/information_schema.result

@@ -1,3 +1,4 @@
+DROP TABLE IF EXISTS t0,t1,t2;
 show variables where variable_name like "skip_show_database";
 Variable_name	Value
 skip_show_database	OFF

mysql-test/t/information_schema.test

@@ -4,6 +4,11 @@
 # Test for information_schema.schemata &
 # show databases
 
+--disable_warnings
+DROP TABLE IF EXISTS t0,t1,t2;
+--enable_warnings
+
+
 show variables where variable_name like "skip_show_database";
 grant select, update, execute on test.* to mysqltest_2@localhost;
 grant select, update on test.* to mysqltest_1@localhost;