mavproxy_link.py: fix websocket output sending mavlink pkt during hanshake

[Huibean]

wsproto.utilities.LocalProtocolError: Event BytesMessage(data=bytearray(b'\xfd\x0f\x00\x00$\x01\x01\x82\x01\x00}\x04\x04\x98\xff\x00\x00\x07\xcb\x92\xb8G\x00\x00\xcc\xd5\xb4'), frame_finished=True, message_finished=True) cannot be sent during the handshake

fix raised error when sending mavlink packet during websocket handshake

[tpwrules]

Wouldn't this be better to do in the write method (which I assume is in mavproxy)?

[Huibean]

Wouldn't this be better to do in the write method (which I assume is in mavproxy)?

Hi @tpwrules ,thanks for you remind, write seems in pymavlink, I am looking forward if I can locate it

[Huibean]

I think better stay current commit, overwrite the write function could blocking mavproxy sending data through handshake

[tpwrules]

How about the open function? I think it makes sense to wait until the handshake is complete there. That is how normal TCP sockets work right?

[peterbarker]

I've merged this one. There might be a better way to do this, but the effects of this change can clearly be seen

Thanks @Huibean @tpwrules