Fix Groups::UpdateService#execute not returning correct error code

This was causing problems in EE, where audit events were being
generated even if the project failed to save.

app/services/groups/update_service.rb

@@ -14,9 +14,11 @@ module Groups
       group.assign_attributes(params)
 
       begin
-        after_update if group.save
+        success = group.save
 
-        true
+        after_update if success
+
+        success
       rescue Gitlab::UpdatePathError => e
         group.errors.add(:base, e.message)
 

spec/services/groups/update_service_spec.rb

@@ -24,6 +24,12 @@ describe Groups::UpdateService do
 
           expect(TodosDestroyer::GroupPrivateWorker).not_to receive(:perform_in)
         end
+
+        it "returns false if save failed" do
+          allow(public_group).to receive(:save).and_return(false)
+
+          expect(service.execute).to be_falsey
+        end
       end
 
       context "internal group with internal project" do