Wrong URL used for "Install" and "Details" buttons on "Add Extensions" admin page

When I setup xwiki on tomcat running on localhost:8080 and nginx in front of it rewriting and proxying everything down to https to tomcat I get a error when clicking on the buttons mentioned in the Summary.

What happens is that it uses http instead of https which causes nginx to redirect it to https and then it fails.

in xwiki.cfg I have:
xwiki.url.protocol=https

my nginx /etc/nginx/sites-enabled/default config
http://paste.ubuntu.com/1389016/

I tried with the help of cjd to debug it but was asked to report this bug.