Autosave the EMS's provider to allow delegates

Delegating things like endpoints, name, and zone to the provider only
works when the base relation has autosave => true

app/models/ext_management_system.rb

@@ -68,7 +68,7 @@ def self.create_from_params(params, endpoints, authentications)
     end
   end
 
-  belongs_to :provider
+  belongs_to :provider, :autosave => true
   has_many :child_managers, :class_name => 'ExtManagementSystem', :foreign_key => 'parent_ems_id'
 
   belongs_to :tenant