We always use delivery_email to generate gravatar_url, but in
test_admin_api_hide_emails we were passing email to get_gravatar_url
and matched with the avatar_url field of the fetched user object.
The tests were passing because the email_address_is_realm_public
was using old realm object and thus email field was incorrectly
set to delivery_email even when email_address_visibility was set
to EMAIL_ADDRESS_VISIBILITY_ADMINS.
This commit fixes the test to pass delivery_email to get_gravatar_url.
9a03a78e3d