Get rid of the delay in onDone event in SocketThreadBase

[tompaana]

We use one second delay to emit onDone event in SocketThreadBase (see onStreamCopyingThreadDone method) to make sure all the data is flushed after we get the end of the stream. This is a nasty workaround which should be removed after we find a proper solution to the problem.

Use unit test case "Test updating advertising and parallel data transfer" to verify the fix.