fix: handle stop server

[vansangpfiev]

http connection closes when we send stop to server

.\cortex-cpp.exe stop
20240829 08:20:13.669000 UTC 6056 WARN  HTTP error: Failed to read connection - stop_server_cmd.cc:16

should do it better

.\cortex-cpp.exe stop
20240829 08:31:55.266000 UTC 12584 INFO  {"message":"Program is exitting, goodbye!"} - stop_server_cmd.cc:13