cluster: fix error on worker disconnect/destroy

Avoid sending multiple `exitedAfterDisconnect` messages when
concurrently calling `disconnect()` and/or `destroy()` from the worker
so `ERR_IPC_DISCONNECTED` errors are not generated.

Fixes: https://github.com/nodejs/node/issues/32106

PR-URL: https://github.com/nodejs/node/pull/32793


Reviewed-By: Zeyu Yang <himself65@outlook.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>