test: dynamic port in cluster worker send

Remove common.PORT from test-cluster-send-deadlock and
test-cluster-send-handle-twice to reduce possibility that
a dynamic port used in another test will collide with common.PORT.

PR-URL: https://github.com/nodejs/node/pull/12472
Ref: https://github.com/nodejs/node/issues/12376


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>