obfsproxy's SOCKS server should send success response post handshake

Currently the obfsproxy SOCKS server sends the response back to tor immediately after the TCP/IP connection has been established, instead of after the underlying transport has been fully initialized.

This behavior is incorrect, and should be changed to each of the underlying transports signalling that they are ready to relay data after they manage to handshake.

With the current SOCKSv4Protocol based listener this would require further monkey patching which may be a good argument for defering this till after #9221 (closed) or similar gets merged.