Don't reject header connections for duplex servers
Don't reject header connections for duplex servers

Summary: Only header is supported by duplex servers.

Differential Revision: D37758718

fbshipit-source-id: 972f9cae506429d378d5e7e9fdd8a726f4e4ee1e

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift