Another checkpoint

Better debug messages. Last four makes the problem evident. We
read a FEATURES_REPLY from the client (the real switch) with
MD5 cca8 but send a FEATURES_REPLY to POX with MD5 28f2.

@jnfoster

    $ make && ./Hypervisor.byte local 6634
    ocaml setup.ml -build
    Finished, 0 targets (0 cached) in 00:00:00.
    Finished, 154 targets (144 cached) in 00:00:03.
    2013-12-25 19:32:48.271358-05:00 Debug new client 127.0.0.1:42769
    2013-12-25 19:32:48.271400-05:00 Info switch connected
    2013-12-25 19:32:48.277543-05:00 Debug new connection 127.0.0.1:43016 (peer is 127.0.0.1:6634)
    2013-12-25 19:32:48.277577-05:00 Info connected to controller
    2013-12-25 19:32:48.277595-05:00 Debug [127.0.0.1:42769] read message: ((version 1) (type_code 0) (xid 111) (body <opaque>))
    hash: 40fd679201e58bd3489ee7a5a5430431
    2013-12-25 19:32:48.278784-05:00 Debug [127.0.0.1:43016] write message: ((version 1) (type_code 0) (xid 111) (body <opaque>))
    hash: 40fd679201e58bd3489ee7a5a5430431
    2013-12-25 19:32:48.298772-05:00 Debug [127.0.0.1:43016] read message: ((version 1) (type_code 0) (xid 7) (body <opaque>))
    hash: 417df90bc80c194c0b8e8c68f9ab277c
    2013-12-25 19:32:48.299227-05:00 Debug [127.0.0.1:42769] write message: ((version 1) (type_code 0) (xid 7) (body <opaque>))
    hash: 417df90bc80c194c0b8e8c68f9ab277c
    2013-12-25 19:32:48.300526-05:00 Debug [127.0.0.1:43016] read message: ((version 1) (type_code 5) (xid 8) (body <opaque>))
    hash: 86243d461b92a653837ad28e59c6c6f0
    2013-12-25 19:32:48.300831-05:00 Debug [127.0.0.1:42769] write message: ((version 1) (type_code 5) (xid 8) (body <opaque>))
    hash: 86243d461b92a653837ad28e59c6c6f0
    2013-12-25 19:32:48.301822-05:00 Debug [127.0.0.1:42769] read message: ((version 1) (type_code 6) (xid 8) (body <opaque>))
    hash: cca8604b57bbfe539733e9bc83528096
    2013-12-25 19:32:48.302149-05:00 Debug [127.0.0.1:43016] write message: ((version 1) (type_code 6) (xid 8) (body <opaque>))
    hash: 28f22d4c9439aa31fd19649ece12f943