These are some changes to help us support infinite scroll in Jetpack.

Specifically this:

• Ensures orderby cannot be empty on a clean install
• Rather than unhooking product query after wp, or after it runs, it only unhooks after pre_get_posts has worked it’s magic.

The queries ran by infinite scroll run too late without these changes leading to odd results.

True compatibility also requires some changes in Infinite scroll so this is not testable alone.

cc @tiagonoronha