Execute `woocommerce_order_action_{$action}` only once

Prevents a “Maximum function nesting level reached” fatal error in certain cases.

Since this ends up running on `'save_post'`, updating something like the order status while hooked onto to `woocommerce_order_action_{$action}` causes a fun recursion :)

I'm not 100% sure if this change will have other implications I have not thought of so feel free to close without merging. I ran into it while testing a code snippet for Customer/Order CSV Export, so I can always adjust that code snippet to only run the first time.