Fix rcu_domain move-assignment pointer copy
Fix rcu_domain move-assignment pointer copy

Summary: [Folly] Fix `rcu_domain` move-assignment pointer copy which seemingly should be a pointer exchange.

Reviewed By: magedm

Differential Revision: D9846892

fbshipit-source-id: ef3a113780af7456d66dacd376b3bf43670fcb9e

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly