Using `folly::AsyncSocket::isClosedByPeer()` instead of `closeReason_` to
Using `folly::AsyncSocket::isClosedByPeer()` instead of `closeReason_` to

Reviewed By: xiaosophiawang

Differential Revision: D2500991

fb-gh-sync-id: 04b9d7242b2848d0b95e9d0afa82415bec7c7502

Orvid/proxygen,LilMeyer/proxygen,Orvid/proxygen,LilMeyer/proxygen,LilMeyer/proxygen,Orvid/proxygen,LilMeyer/proxygen,Orvid/proxygen