Fix issue displaying completed orders in admin

[dougjohnston]

Fixes an issue where checking the 'only show complete orders' checkbox
and then unchecking it was no longer displaying completed orders.

A similar fix was merged into Spree after the Solidus fork:
spree/spree@69a20c3

[jhawthorn]

👍 Thank you. The test case is especially appreciated 😄

This changes the behaviour when "only show complete orders" from displaying only incomplete orders to showing both complete and incomplete orders. We'll have to add this to our changelog.

[dougjohnston]

It fixes behavior more than changes it.

When initially loading the order admin page, complete and incomplete orders are shown. That's expected. Clicking the 'only show complete order' checkbox removes the incomplete orders and shows only completed orders. Also expected.

If I then uncheck the box, I would expect it to show complete and incomplete orders again, but it was only showing incomplete orders. That's not expected (to me at least 😄 ) and that's the behavior this PR fixes.

Perhaps it still warrants a note in the changelog. Do you want me to add that? Or, will you add it?

[dougjohnston]

I see now that the naming of my test doesn't make sense within the context I put it in. I'll fix that.

[jhawthorn]

Do you want me to add that? Or, will you add it?

I'm happy to fill in the changelog, but help is always appreciated 😄

[cbrunsdon]

Yea, looks good to me, thanks a lot @dougjohnston 👍