remove some redundant or pessimizing std::move
remove some redundant or pessimizing std::move

Summary: Remove some std::move detected by clang's `-Wmove`.

Reviewed By: yfeldblum

Differential Revision: D2619980

fb-gh-sync-id: 333477227d4b8c14282e65d4d2e3747f8cb29fd9

ldemailly/wdt,luluandleilei/wdt,ldemailly/wdt,luluandleilei/wdt,luluandleilei/wdt,ldemailly/wdt,ldemailly/wdt,luluandleilei/wdt