lxc-alpine: use yaml for detection of latest release
lxc-alpine: use yaml for detection of latest release

Alpine Linux provides yaml files with latest release instead of the old
approach with .latest.txt.

Signed-off-by: Natanael Copa <d6dfbe96822fc6f407d114112670f8d1571509f1@alpinelinux.org>
Acked-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>

bmoar/lxc,bostjan/lxc,ysbnim/lxc,raspberrypython/lxc,regit/lxc,bostjan/lxc,ysbnim/lxc,hallyn/lxc,terceiro/lxc,cjwatson/lxc,ksperis/lxc,cjwatson/lxc,aeris/lxc,hallyn/lxc,bmoar/lxc,ss1h2a3tw/lxc,QingweiPeterLan/cs188-lxc,efiop/lxc,fwilson42/lxc,rowhit/lxc,Pelagicore/lxc,armcc/lxc,LynxChaus/lxc,virajs/lxc,jirislaby/lxc,major/lxc,sapun/lxc,DarknessBeforeDawn/lxc,fwilson42/lxc,sapun/lxc,codebauss/lxc,codebauss/lxc,codebauss/lxc,Ponce/lxc,hfuCN/lxc,akshaykarle/lxc,JohnPeacockMessageSystems/lxc,aeris/lxc,caglar10ur/lxc,jirislaby/lxc,szaszg/lxc,caglar10ur/lxc,lazy404/lxc,tych0/lxc,caglar10ur/lxc,ecarrara/lxc,cjwatson/lxc,yubo/lxc,lisongmin/lxc,Ponce/lxc,akshaykarle/lxc,federicobriata/lxc,ksperis/lxc,efiop/lxc,ksperis/lxc,szaszg/lxc,lazy404/lxc,rowhit/lxc,ysbnim/lxc,major/lxc,rldleblanc/lxc,GreatFruitOmsk/lxc,rldleblanc/lxc,armcc/lxc,Ponce/lxc,jirislaby/lxc,regit/lxc,Pelagicore/lxc,terceiro/lxc,ecarrara/lxc,JohnPeacockMessageSystems/lxc,akshaykarle/lxc,tych0/lxc,yubo/lxc,christiaan/lxc,ss1h2a3tw/lxc,major/lxc,szaszg/lxc,ss1h2a3tw/lxc,raspberrypython/lxc,JohnPeacockMessageSystems/lxc,thmo/lxc,sapun/lxc,tych0/lxc,Pelagicore/lxc,christiaan/lxc,Distrotech/lxc,hkjolhede/lxc,ioops/lxc,Distrotech/lxc,efiop/lxc,hallyn/lxc,DarknessBeforeDawn/lxc,bostjan/lxc,QingweiPeterLan/cs188-lxc,QingweiPeterLan/cs188-lxc,hkjolhede/lxc,hfuCN/lxc,yubo/lxc,fwilson42/lxc,Distrotech/lxc,ioops/lxc,GreatFruitOmsk/lxc,bmoar/lxc,hkjolhede/lxc,rldleblanc/lxc,regit/lxc,hfuCN/lxc,terceiro/lxc,DarknessBeforeDawn/lxc,raspberrypython/lxc,rowhit/lxc,federicobriata/lxc,lisongmin/lxc,ecarrara/lxc,lazy404/lxc,lisongmin/lxc,federicobriata/lxc,aeris/lxc,LynxChaus/lxc,thmo/lxc,LynxChaus/lxc,virajs/lxc,virajs/lxc,armcc/lxc,thmo/lxc,ioops/lxc,GreatFruitOmsk/lxc,christiaan/lxc