selftests/user_events: Add test cases when event is disabled

When user_events are disabled, it's write operation should return -EBADF.
Add this test cases.

Link: https://lkml.kernel.org/r/20230626111344.19136-4-sunliming@kylinos.cn

Acked-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: sunliming <sunliming@kylinos.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>