cannot update role permission for the same session

[HarrisChu]

Currently, we verify the role permission in graphd.

steps:

1. create a user A with admin role.
2. login with the user A, and do not release the session.
3. login with root in another session.
4. change role from admin to user.

expected:

1. the original session cannot create schema.

actual:

1. still could create schema, as we use roles when the user login.