net: allow cluster workers to listen on exclusive ports

Currently, all `listen()` calls go through the cluster master. This commit allows workers to listen on ports exclusively. Closes #3856
The `util.isObject(arguments[0])` check on line 1199 verifies that the first argument is an object. From there, a different `if` statement parses the various possible object types, with the final `else` throwing. The top level `else` is already used for a different interpretation of the input arguments.