User can not kill it own session with 'kill' cmd

[morningman]

Describe the bug
User can not kill it own session with 'kill' cmd

To Reproduce

1. connect to doris with a non-root user;
2. connect to doris use same user from different host
3. execute 'show processlist' and try to kill the first connect with 'kill connect_id';
4. error: ERROR 1095 (HY000): You are not owner of thread 61711

Expected behavior
User should be able to kill its own connections.

[morningman]

Now, only admin and root user can kill connection.