Ensure posix_spawn is used to execute ping when available

We want to avoid the memory copy when possible, and python
will not try posix_spawn unless close_fds=False

https://github.com/rtomayko/posix-spawn#linux

esphome/dashboard/dashboard.py

@@ -1068,6 +1068,7 @@ async def _async_ping_host(host: str) -> bool:
         stdin=asyncio.subprocess.DEVNULL,
         stdout=asyncio.subprocess.DEVNULL,
         stderr=asyncio.subprocess.DEVNULL,
+        close_fds=False,  # Required for posix_spawn
     )
     await process.wait()
     return process.returncode == 0