show grants return wrong result.

[crazycs520]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Create user, role.

CREATE ROLE 'app_read';
create user test@'%';
GRANT SYSTEM_VARIABLES_ADMIN, PROCESS on *.* to 'app_read'@'%';
GRANT 'app_read' TO 'test'@'%';
SET DEFAULT ROLE app_read TO 'test'@'%';

2. What did you expect to see? (Required)

▶ mysql -u test -h 127.0.0.1 -P 4000
(none)> show grants;
+---------------------------------------------------+
| Grants for test@%                                 |
+---------------------------------------------------+
| GRANT PROCESS ON *.* TO `test`@`%`                |
| GRANT SYSTEM_VARIABLES_ADMIN ON *.* TO `test`@`%` |
| GRANT `app_read`@`%` TO `test`@`%`                |
+---------------------------------------------------+
3 rows in set
Time: 0.008s
(none)> show grants for current_user();
+---------------------------------------------------+
| Grants for test@%                                 |
+---------------------------------------------------+
| GRANT PROCESS ON *.* TO `test`@`%`                |
| GRANT SYSTEM_VARIABLES_ADMIN ON *.* TO `test`@`%` |
| GRANT `app_read`@`%` TO `test`@`%`                |
+---------------------------------------------------+
3 rows in set

3. What did you see instead (Required)

▶ mysql -u test -h 127.0.0.1 -P 4000
(none)> show grants;
+------------------------------------+
| Grants for User                    |
+------------------------------------+
| GRANT PROCESS ON *.* TO 'test'@'%' |
| GRANT 'app_read'@'%' TO 'test'@'%' |
+------------------------------------+
2 rows in set
Time: 0.008s
(none)> show grants for current_user();
+------------------------------------+
| Grants for test@127.0.0.1          |
+------------------------------------+
| GRANT USAGE ON *.* TO 'test'@'%'   |
| GRANT 'app_read'@'%' TO 'test'@'%' |
+------------------------------------+

4. What is your TiDB version? (Required)

***************************[ 1. row ]***************************
tidb_version() | Release Version: v5.2.0-alpha-601-gce60af56e
Edition: Community
Git Commit Hash: ce60af56ea2bf28b72986dcb6e6e3300720186c8
Git Branch: master
UTC Build Time: 2021-08-13 10:53:04
GoVersion: go1.16.6
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[crazycs520]

@morgo PTAL

[ti-srebot]

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