Fix a security issue (!) in link handshake validation.

When making sure that the peer had the right RSA identity, we
were comparing the RSA identity with itself, not with the RSA
identity we expected.

Found via unit testing (!).

tor-proto/src/channel/handshake.rs

@@ -344,7 +344,7 @@ impl<T: AsyncRead + AsyncWrite + Send + Unpin + 'static> UnverifiedChannel<T> {
             return Err(Error::ChanProto("Peer ed25519 id not as expected".into()));
         }
 
-        if pkrsa.to_rsa_identity() != rsa_id {
+        if *peer.rsa_identity() != rsa_id {
             return Err(Error::ChanProto("Peer RSA id not as expected".into()));
         }