Fixes #7045 - fix location undefined for user

Fix issue where location is undefined for User in find_only_environment
of the system api. Also remove un-needed logic in find_only_environment.
I could probably just write this as:

```
def find_environment_and_content_view
  if !params.key?(:environment_id)
    @environment = @organization.library if @organization
  else
    find_environment_and_content_view_by_env_id
  end
end