Various fixes for bootstrap image download via HTTPS
Various fixes for bootstrap image download via HTTPS

- Make sure mirror URL is queried for $FEDORA_RELEASE_DEFAULT
- Fix image path for URLs queried via mirror list

Signed-off-by: Reto Gantenbein <192e2b4def8f7964936fd2f4aadf1f9332bed3b1@linuxmonk.ch>

hallyn/lxc,hallyn/lxc,GreatFruitOmsk/lxc,caglar10ur/lxc,ss1h2a3tw/lxc,aeris/lxc,GreatFruitOmsk/lxc,terceiro/lxc,caglar10ur/lxc,thmo/lxc,terceiro/lxc,terceiro/lxc,federicobriata/lxc,federicobriata/lxc,hallyn/lxc,thmo/lxc,aeris/lxc,LynxChaus/lxc,aeris/lxc,caglar10ur/lxc,ysbnim/lxc,LynxChaus/lxc,ysbnim/lxc,federicobriata/lxc,GreatFruitOmsk/lxc,ss1h2a3tw/lxc,LynxChaus/lxc,ss1h2a3tw/lxc,ysbnim/lxc,thmo/lxc