test: add cluster EADDRINUSE test
test: add cluster EADDRINUSE test

Check that having a worker bind to a port that's already taken doesn't
leave the master process in a confused state. Releasing the port and
trying again should Just Work[TM].

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node