We should only keep tests for changing email_address_visibility in
test_realm.py. The tests for checking the value of delivery_email
and email in the user dicts returned by 'GET users/{user_id}'
endpoint according to email_address_visibility should be in
test_users.py and not test_realm.py.
The tests of other realm settings are also arranged in the same way.
This commit makes the test more robust by checking for all
possible values of email_address_visibility and checking
emails and delivery emails values received by different
user roles.