EWW problems with SNI https sites?

[Hideki Saito <hidekis@gmail.com>]

Hello,
I'm having a bit of problem with EWW accessing some sites under Windows,
namely, some sites returning "400 Bad Request" -- the reason being "The
plain HTTP request was sent to HTTPS port"

This seems to affect a lot of CloudFlare hosted sites. But even without
CloudFlare, this seems to be affecting SNI (Server Name Indication -- ones
without dedicated IP address) hosts as well.

Here's the pattern I'm seeing:
1) https://www.hidekisaito.com (CloudFlare) -- doesn't work
2) https://hidekisaito.com (SNI) -- doesn't work
3) https://duckduckgo.com -- works
4) https://twitter.com -- works
5) https://helpa.hidekisaito.com (SNI) -- doesn't work (due to the
maintenance, the site might be down for next few hours.

I have my personal ELPA site on #5 site, and this seems to be causing
issue; M-x list-package fails with the same error, M-x
package-refresh-content somehow successfully fetch the list. (But doesn't
help as fetching and installing the package would fail with 400 Bad Request)

I can live with eww not working, but it's painful that list-package doesn't
work. Do you happen to know if there are anyways to force list-package (and
package download) to use the method used by package-refresh-content?

Please let me know if this is something I should be reporting as a bug.

Thank you.

Hideki Saito (斉藤英樹)