commit 5b9c420c introduced some undesirable behaviour with packet send
functions returning error when they shouldn't. We now only return an
error if the packet fails to be added to the send queue or cannot
be wrapped/encrypted. We no longer error if we fail to send the packet
over the wire, because toxcore will keep trying to re-send the packet
until the connection times out.
Additionally, we now make sure that our packet broadcast functions
aren't returning an error when failing to send packets to peers
that we have not successfully handshaked with yet, since this is
expected behaviour.
