remove invalid test

it starts an EXPLAIN of a multi-table join and tries to KILL it.
no sync points.
depending on how fast the hareware is and optimizer development
it might kill EXPLAIN at some random point in time (generally unrelated
to the Bug#28598 it was supposed to test) or EXPLAIN might finish
before the KILL and the test will fail.

mysql-test/main/kill.result

@@ -197,20 +197,6 @@ f2
 connection default;
 SET DEBUG_SYNC = 'RESET';
 DROP TABLE t1, t2;
-connection con1;
-connection con2;
-connection con1;
-SET SESSION optimizer_search_depth=0;
-SET DEBUG_SYNC= 'before_join_optimize SIGNAL in_sync';
-PREPARE stmt FROM 'EXPLAIN SELECT * FROM t1,t2,t3,t4,t5,t6,t7,t8,t9,t10,t11,t12,t13,t14,t15,t16,t17,t18,t19,t20,t21,t22,t23,t24,t25,t26,t27,t28,t29,t30,t31,t32,t33,t34,t35,t36,t37,t38,t39,t40 WHERE a1=a2 AND a2=a3 AND a3=a4 AND a4=a5 AND a5=a6 AND a6=a7 AND a7=a8 AND a8=a9 AND a9=a10 AND a10=a11 AND a11=a12 AND a12=a13 AND a13=a14 AND a14=a15 AND a15=a16 AND a16=a17 AND a17=a18 AND a18=a19 AND a19=a20 AND a20=a21 AND a21=a22 AND a22=a23 AND a23=a24 AND a24=a25 AND a25=a26 AND a26=a27 AND a27=a28 AND a28=a29 AND a29=a30 AND a30=a31 AND a31=a32 AND a32=a33 AND a33=a34 AND a34=a35 AND a35=a36 AND a36=a37 AND a37=a38 AND a38=a39 AND a39=a40  ';
-EXECUTE stmt;
-connection con2;
-SET DEBUG_SYNC= 'now WAIT_FOR in_sync';
-KILL QUERY @id;
-connection con1;
-ERROR 70100: Query execution was interrupted
-connection default;
-SET DEBUG_SYNC = 'RESET';
 #
 # Bug#19723: kill of active connection yields different error code
 # depending on platform.

mysql-test/main/kill.test

@@ -272,74 +272,6 @@ connection default;
 SET DEBUG_SYNC = 'RESET';
 DROP TABLE t1, t2;
 
-#
-# Bug#28598: mysqld crash when killing a long-running explain query.
-#
-connection con1;
-let $ID= `SELECT @id := CONNECTION_ID()`;
-connection con2;
-let $ignore= `SELECT @id := $ID`;
-connection con1;
---disable_query_log
-let $tab_count= 40;
-
---disable_query_log
-begin;
-let $i= $tab_count;
-while ($i)
-{
-  eval CREATE TABLE t$i (a$i INT, KEY(a$i));
-  eval INSERT INTO t$i VALUES (1),(2),(3),(4),(5),(6),(7);
-  dec $i ;
-}
-
-commit;
---enable_query_log
-
-SET SESSION optimizer_search_depth=0;
-
-let $i=$tab_count;
-while ($i)
-{
-  let $a= a$i;
-  let $t= t$i;
-  dec $i;
-  if ($i)
-  {
-    let $comma=,;
-    let $from=$comma$t$from;
-    let $where=a$i=$a $and $where;
-  }
-  if (!$i)
-  {
-    let $from=FROM $t$from;
-    let $where=WHERE $where;
-  }
-  let $and=AND;
-}
-
---enable_query_log
-SET DEBUG_SYNC= 'before_join_optimize SIGNAL in_sync';
-eval PREPARE stmt FROM 'EXPLAIN SELECT * $from $where';
-send EXECUTE stmt;
-
-connection con2;
-SET DEBUG_SYNC= 'now WAIT_FOR in_sync';
-KILL QUERY @id;
-connection con1;
---error 1317
-reap;
---disable_query_log
-let $i= $tab_count;
-while ($i)
-{
-  eval DROP TABLE t$i;
-  dec $i ;
-}
---enable_query_log
-connection default;
-SET DEBUG_SYNC = 'RESET';
-
 --echo #
 --echo # Bug#19723: kill of active connection yields different error code
 --echo # depending on platform.