text: Title: Wrong facet function called when defining a custom group
  Body: ## CKAN version
  2.9, 2.10,  master
  
  ## Describe the bug
  When developer defines a custom group with `group_type` something else than `group`, `group_facets` is not called, instead ckan calls `organization_facets`
  https://github.com/ckan/ckan/blob/71d5d1be495ec9662323eb69d6f71b2ccbb894f2/ckan/views/group.py#L378-L387
  
  ### Steps to reproduce
  Create a custom group with group_type something else than group. Try to update facets of the said group.
  
  ### Expected behavior
  `group_facets` should be called when its not an organization.
  
  
  