Make the logs to be opened after forking when Flexisip has been launched with --daemon option

That fix an issue that lead Flexisip to write its log messages into an already rotated
file (e.g. flexisip-proxy.log.1) when the instance has been respawned after crashing.
10 jobs for fix/open_log_after_spawning
in 15 minutes and 18 seconds and was queued for 2 seconds