Introduce smart timeout loop into launch_fluent

Introduce a smart timeout loop while launching Fluent. When we start a process, we start with the default timeout, then we take the process id and check if the server info file has been generated and updated. If yes, then we increase the default timeout by some amount to wait for the Fluent server to respond, however if the answer is no, then we just exit after the default timeout as Fluent server might have crashed at startup or might not have spawned.

@raph-luc, please feel free to add more details as required. Thank you.

The issue names launch_fluent but does not identify a file or test. Locate the launch_fluent implementation and its existing process timeout and server-info handling first; done means the launch waits longer only when the server info file is updated, while exiting after the default timeout when it is not.

Written by the indexing model from the issue text.