Bug#31608 missing mysqltest change_user command

Post merge fixes: close any open statement before
the change user command and fix test case output.

client/mysqltest.c

@@ -3063,6 +3063,12 @@ void do_change_user(struct st_command *command)
                      sizeof(change_user_args)/sizeof(struct command_arg),
                      ',');
 
+  if (cur_con->stmt)
+  {
+    mysql_stmt_close(cur_con->stmt);
+    cur_con->stmt= NULL;
+  }
+
   if (!ds_user.length)
     dynstr_set(&ds_user, mysql->user);
 

mysql-test/r/change_user.result

@@ -34,8 +34,8 @@ NULL
 SELECT GET_LOCK('bug31418', 1);
 GET_LOCK('bug31418', 1)
 1
-SELECT IS_USED_LOCK('bug31418');
-IS_USED_LOCK('bug31418')
+SELECT IS_USED_LOCK('bug31418') = CONNECTION_ID();
+IS_USED_LOCK('bug31418') = CONNECTION_ID()
 1
 change_user
 SELECT IS_FREE_LOCK('bug31418');

mysql-test/t/change_user.test

@@ -28,7 +28,7 @@ SELECT @@session.sql_big_selects;
 SELECT IS_FREE_LOCK('bug31418');
 SELECT IS_USED_LOCK('bug31418');
 SELECT GET_LOCK('bug31418', 1);
-SELECT IS_USED_LOCK('bug31418');
+SELECT IS_USED_LOCK('bug31418') = CONNECTION_ID();
 --echo change_user
 --change_user
 SELECT IS_FREE_LOCK('bug31418');