test(functional) - Fix users_controller functional test

Following changes were made:
* remove `designation` field, which is not part of users model
* rename `mobile` field to `phone`
* rename `profile_pic` field to `avatar_id`

Note:
All functional test for admin controllers will fail right now. Admin pages
give a 302 if the user isn't authenticated as admin, and so the tests fail.

Testing admin pages must be done with an test admin user. CI tests will
continue to fail until this is resolved.