url: change path parsing for non-special URLs

This changes to the way path parsing for non-special URLs.
It allows paths to be empty for non-special URLs and also
takes that into account when serializing.

PR-URL: https://github.com/nodejs/node/pull/12507
Fixes: https://github.com/nodejs/node/issues/11962
Refs: https://github.com/whatwg/url/pull/213


Reviewed-By: James M Snell <jasnell@gmail.com>