get children on invalidation
get children on invalidation

Summary: When a node was invalidated, not only the node itself needs to be refetched, but also its children.

Reviewed By: jknoxville

Differential Revision: D14280318

fbshipit-source-id: a262a2c95347dc9bf72f83b6a9eba9d3f9badb5a

facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper