15b3 - bug background caching starts during delivery renders

If background caching or auto cache transitions/composites/fusion is enabled - caching renders can start during delivery output renders.
During delivery renders Resolve thinks user activity has timed out and starts Also rendering background cache - causing dropped frames or WHEA on the delivery render.
Thumbnail generation on the delivery page can also happen during delivery render if clips view is enabled, Also potentially causing dropped frames or at least slowing delivery render.
During delivery renders Resolve thinks user activity has timed out and starts Also rendering background cache - causing dropped frames or WHEA on the delivery render.
Thumbnail generation on the delivery page can also happen during delivery render if clips view is enabled, Also potentially causing dropped frames or at least slowing delivery render.