http2: allow port 80 in http2.connect

Due to how WHATWG-URL parser works, port numbers are omitted if
they are the default port for a scheme. This meant that
http2.connect could not accept connections on port 80 with http
scheme. Fix this bug by detecting http: scheme and setting port
to 80.

PR-URL: https://github.com/nodejs/node/pull/16337
Fixes: https://github.com/nodejs/node/issues/14304


Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>