[CustomActionsMixin] Fixes for MiqSetMembership

Mostly converting the previous queries that existed to an AR based
version.

Notably:  The `uniq.flatten` needed to be switched out because previous
an array was returned by `.generic_button_group`, but now an
ActiveRecord::CollectionProxy is returned and if `uniq` is called first,
it doesn't do anything since each `CollectionProxy` is a uniq instance.
Doing a `flatten` first will convert the `CollectionProxy` instances to
Arrays, then the elements can properly have `.uniq` called on them.

app/models/mixins/custom_actions_mixin.rb

@@ -25,19 +25,22 @@ def custom_action_buttons(applies_to = self)
   end
 
   def generic_button_group
-    generic_custom_buttons.select { |button| !button.parent.nil? }
+    generic_custom_buttons.includes(:custom_button_sets)
+                          .select { |button| button.custom_button_sets.present? }
   end
 
   def custom_button_sets_with_generics
-    custom_button_sets + generic_button_group.map(&:parent).uniq.flatten
+    custom_button_sets + generic_button_group.flat_map(&:custom_button_sets).uniq
   end
 
   def custom_buttons
-    generic_custom_buttons.select { |button| button.parent.nil? } + direct_custom_buttons
+    generic_custom_buttons.includes(:custom_button_sets)
+                          .select { |b| b.custom_button_sets.blank? } + direct_custom_buttons
   end
 
   def direct_custom_buttons
-    CustomButton.buttons_for(self).select { |b| b.parent.nil? }
+    CustomButton.buttons_for(self).includes(:custom_button_sets)
+                .select { |b| b.custom_button_sets.blank? }
   end
 
   def filter_by_visibility(buttons, applies_to = self)

spec/models/service_template_spec.rb

@@ -99,7 +99,8 @@
           )
         ]
       }
-      expect(service_template.custom_actions(service)).to match(expected)
+      actual = service_template.custom_actions(service)
+      expect(actual).to match(expected)
     end
 
     context "expression evaluation" do
@@ -183,7 +184,8 @@
           )
         ]
       }
-      expect(service_template.custom_actions(service)).to match(expected)
+      actual = service_template.custom_actions(service)
+      expect(actual).to match(expected)
     end
   end