ignore deleted overrides in has_overrides?

test plan:
* have an overriden assignment
* delete the overrides
* should not return "has_overrides in the API

closes #CORE-3

Change-Id: I14c131226e606bb7493586b417bce2447016bdb8
Reviewed-on: https://gerrit.instructure.com/130170
Tested-by: Jenkins
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Jeremy Putnam <jeremyp@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>

lib/dates_overridable.rb

@@ -60,7 +60,12 @@ module DatesOverridable
   end
 
   def has_overrides?
-    assignment_overrides.loaded? ? assignment_overrides.any? : assignment_overrides.exists?
+    if current_version?
+      assignment_overrides.loaded? ? assignment_overrides.any?(&:active?) : assignment_overrides.active.exists?
+    else
+      # the old version's overrides might have be deleted too but it's probably more trouble than it's worth to check here
+      assignment_overrides.loaded? ? assignment_overrides.any? : assignment_overrides.exists?
+    end
   end
 
   def has_active_overrides?

spec/lib/dates_overridable_spec.rb

@@ -205,6 +205,11 @@ shared_examples_for "an object whose dates are overridable" do
       it { is_expected.to be_truthy }
     end
 
+    context "when it does but it's deleted" do
+      before { override.destroy }
+      it { is_expected.to be_falsey }
+    end
+
     context "when it doesn't" do
       it { is_expected.to be_falsey }
     end