move innodb specific test from group_by.test to group_by_innodb.test

mysql-test/r/group_by.result

@@ -2473,29 +2473,3 @@ c	1c
 v	2v,2v
 NULL	1c,2v,2v
 DROP TABLE t1,t2;
-#
-# Test of MDEV-4002
-#
-CREATE TABLE t1 ( 
-pk INT NOT NULL PRIMARY KEY, 
-d1 DOUBLE, 
-d2 DOUBLE, 
-i INT NOT NULL DEFAULT '0',
-KEY (i)
-) ENGINE=InnoDB;
-INSERT INTO t1 VALUES (1,1.0,1.1,1),(2,2.0,2.2,2);
-PREPARE stmt FROM " 
-SELECT DISTINCT i, GROUP_CONCAT(  d1, d2 ORDER BY d1, d2 ) 
-FROM t1 a1 NATURAL JOIN t1 a2 GROUP BY i WITH ROLLUP 
-";
-EXECUTE stmt;
-i	GROUP_CONCAT(  d1, d2 ORDER BY d1, d2 )
-1	11.1
-2	22.2
-NULL	11.1,22.2
-EXECUTE stmt;
-i	GROUP_CONCAT(  d1, d2 ORDER BY d1, d2 )
-1	11.1
-2	22.2
-NULL	11.1,22.2
-DROP TABLE t1;