openSUSE: don't use https to access mirrors for the time being

openSUSE: don't use https to access mirrors for the time being

Some openSUSE mirrors redirect https to http and this seems to make
curl(1) unhappy now.

There's a request to fix that on mirror side:
https://github.com/openSUSE/mirrorbrain/issues/3 but for the time
being switch to http to access all mirrors.

There seems to be no additional values in https:// as the rpms are
signed by gpg keys already, so is the repodata anyways.

Fixes: #137
Fixes: #159