Cut TAsyncSocket::HandshakeCallback
Cut TAsyncSocket::HandshakeCallback

Summary: [Thrift] Cut `TAsyncSocket::HandshakeCallback`, which is just a thin wrapper around `folly::AsyncSSLSocket::HandshakeCB`.

Reviewed By: iahs

Differential Revision: D21971059

fbshipit-source-id: 162c0d3330ed6735e844ef33bcefda3d1d9a85b8

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