Fixed MDEV-8428: Mangled DML statements on 2nd level slave when enabling binlog checksums

Fix was to add a test in Query_log_event::Query_log_event() if we are using
CREATE ... SELECT and in this case use trans cache, like we do on the master.
This avoid using (with doesn't have checksum)

Other things:
- Removed dummy call my_checksum(0L, NULL, 0)
- More DBUG_PRINT
- Cleaned up Log_event::need_checksum() to make it more readable (similar as in MySQL 5.6)
- Renamed variable that was hiding another one in create_table_imp()

mysql-test/suite/rpl/r/create_select.result

@@ -0,0 +1,30 @@
+include/rpl_init.inc [topology=1->2->3]
+# On server_1
+CREATE DATABASE test_8428;
+USE test_8428;
+CREATE TABLE t1(i INT) ENGINE=INNODB;
+INSERT INTO t1 VALUES(1), (2), (3), (4), (5);
+CREATE TABLE t2 AS SELECT * FROM t1;
+CREATE TABLE t3 ENGINE=MyISAM AS SELECT * FROM t1;
+# On server_2
+SHOW TABLES IN test_8428;
+Tables_in_test_8428
+t1
+t2
+t3
+# On server_3
+SHOW TABLES IN test_8428;
+Tables_in_test_8428
+t1
+t2
+t3
+SELECT * from test_8428.t1;
+i
+1
+2
+3
+4
+5
+DROP DATABASE test_8428;
+include/rpl_end.inc
+# End of test