Merge branch '28850-fix-broken-migration' into 'master'

Disable the inheritance column of services in DisableInvalidServiceTemplates migration

Closes #28850

See merge request !9613

changelogs/unreleased/28850-fix-broken-migration.yml

+---
+title: Fix broken migration when upgrading straight to 8.17.1
+merge_request: 9613
+author:

db/post_migrate/20170211073944_disable_invalid_service_templates.rb

 class DisableInvalidServiceTemplates < ActiveRecord::Migration
   DOWNTIME = false
 
-  unless defined?(Service)
-    class Service < ActiveRecord::Base
-      self.inheritance_column = nil
-    end
+  class Service < ActiveRecord::Base
+    self.inheritance_column = nil
   end
 
   def up