message: Fix handshake_encoding/decoding tests
  Comparing Handshake::default() against HANDSHAKE_BYTES is annoying
  since then we'll have to update HANDSHAKE_BYTES every time we add a
  handler. So instead just test whether they both round-trip correctly.
diff: @@ -384,17 +384,14 @@ mod tests {
  #[test]
  fn handshake_decoding() {
  - let hs = Handshake::default();
  -
  - let hs_ : Handshake = RawCbor::from(HANDSHAKE_BYTES).deserialize().unwrap();
  - println!("");
  + let hs : Handshake = RawCbor::from(HANDSHAKE_BYTES).deserialize().unwrap();
  println!("{}", hs.in_handlers);
  - println!("{}", hs_.in_handlers);
  - assert_eq!(hs.protocol_magic, hs_.protocol_magic);
  - assert_eq!(hs.version, hs_.version);
  - assert_eq!(hs.in_handlers, hs_.in_handlers);
  - assert_eq!(hs.out_handlers, hs_.out_handlers);
  - assert_eq!(hs, hs_);
  +
  + assert_eq!(hs.protocol_magic, ProtocolMagic::default());
  + assert_eq!(hs.version, block::Version::default());
  +
  + let hs_ = cbor!(&hs).unwrap();
  + assert_eq!(HANDSHAKE_BYTES, hs_.as_slice());
  }
  #[test]
  @@ -402,6 +399,8 @@ mod tests {
  let hs = Handshake::default();
  let vec = cbor!(&hs).unwrap();
  - assert_eq!(HANDSHAKE_BYTES, vec.as_slice());
  +
  + let hs_ : Handshake = RawCbor::from(&vec).deserialize().unwrap();
  + assert_eq!(hs, hs_);
  }
  }
  