The root cause is actually that the agent's streaming HTTP API didn't flush until the first log line was found which commonly was pretty soon since the default level is INFO. In cases where there were no logs immediately due to level for instance, the client gets stuck in the HTTP code waiting on a response packet from the server before we enter the loop that checks the shutdown channel from the signal handler.
This fix flushes the initial status immediately on the streaming endpoint which lets the client code get into it's expected state where it's listening for shutdown or log lines.
69ebbf3e79