When creating or changing a user in the frontend the "Permissions" tab shows a preview of the permissions the user will be granted. But when the user's groups are changed in the form the permission preview is not updated accordingly. This only happens after removing and re-assigning the user's role.

Steps to reproduce:

1. Go to Users -> Users -> Create user
2. Assign a user group granting access to some host group.
3. Switch to the "Permissions" tab.
4. Assing a role.
5. Switch to the "User" tab.
6. Replace the user group by another one granting access to a different host group.
7. Switch back to the "Permissions" tab.
8. The permissions shown are still the same as before replacing the user group.
9. Unassign and re-assign the role.
10. The permissions are updated and shown correctly.