test: refactor test-cluster-send-deadlock

Wait for the sockets to be connected before closing them and remove
unneeded `setTimeout()`.

PR-URL: https://github.com/nodejs/node/pull/19241


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>