prepared statements spend a lot of time in cleanup

--- a/mysql-test/main/mysql_client_test.test

+++ b/mysql-test/main/mysql_client_test.test

@@ -26,7 +26,7 @@ call mtr.add_suppression(" IP address .* could not be resolved");

 # var/log/mysql_client_test.trace

 --exec echo "$MYSQL_CLIENT_TEST" > $MYSQLTEST_VARDIR/log/mysql_client_test.out.log 2>&1

---exec $MYSQL_CLIENT_TEST --getopt-ll-test=25600M >> $MYSQLTEST_VARDIR/log/mysql_client_test.out.log 2>&1

+--exec $MYSQL_CLIENT_TEST test_mdev_16128 --getopt-ll-test=25600M >> $MYSQLTEST_VARDIR/log/mysql_client_test.out.log 2>&1

 # End of 4.1 tests

 echo ok;

--- a/tests/mysql_client_test.c

+++ b/tests/mysql_client_test.c

@@ -21053,6 +21053,7 @@ static void test_mdev_16128()

   rc= mysql_stmt_prepare(stmt, query, strlen(query));

   check_execute(stmt, rc);

+for (uint ii=0; ii < 10000; ii++) {

   memset(&bind, 0, sizeof(bind));

   bind.buffer_type= MYSQL_TYPE_STRING;

   bind.buffer_length= strlen(bind_arg_1);

@@ -21109,6 +21110,7 @@ static void test_mdev_16128()

     executed in PS-mode and bound with the value 'd' returns empty result set.

    */

   DIE_UNLESS(rc == MYSQL_NO_DATA);

+}

   mysql_stmt_close(stmt);