KRPC-97 Race condition in stream cancellation locks the transport

[Mr3zee]

Subsystem
Stream cancellation

Problem Description
There might be a race condition between StreamEnd and StreamCancel messages, resulting in a deadlock in

public suspend fun cancelStream(message: RPCCallMessage.StreamCancel) {
    incomingChannelOf(message.streamId).send(StreamCancel(message.cause.deserialize()))
}

incomingChannelOf waits for the cannel that was already removed and will never be present

Solution
Added a closedStreams set that checks for such already closed streams and if on is closed - does not wait to close it once again