Add support for qcow2 images in $IMAGE_URLS.
Add support for qcow2 images in $IMAGE_URLS.

This patch adds support for loading a qcow2 image and using the 'bare'
container format for all single file images.

I tested this successfully by setting:

IMAGE_URLS="http://berrange.fedorapeople.org/images/2012-02-29/f16-x86_64-openstack-sda.qcow2"

Change-Id: Ia55ffd4957866a3d7b9fd7ba4c62e38663b35080

r-mibu/devstack,nuxeh/devstack,j4/devstack,prithivm/branch01,promptworks/devstack,flavio-fernandes/devstack,Millnert/contrail-devstack,nttmcl/devstack_public,avvocatodemarchis/devstack,j4/devstack,prithivm/branch01,avvocatodemarchis/devstack,pombredanne/devstack,mc2014/devstack,liuquansheng47/devstack,parul24/devstack,shootstar/devstacktest,vishnugonela/devstack,yamt/devstack,bq-xiao/devstack,bigswitch/devstack,Mahito/devstack,noironetworks/devstack,CiscoSystems/devstack,olivierlemasle/devstack,nawawi/openstack,thomasem/devstack,CloudServer/devstack,pacinete/devstack,upadhyay-prashant/devstack,williamthegrey/devstack,costingalan/devstack,eshnil2000/devstack,nuxeh/devstack,affo/devstack,innodee/openstackk,sequenceiq/devstack,richliu/devstack,cloudbuilders/devstack,herrsechs/devstack,atulpatil301/devstack,dirkmueller/devstack,openstack-dev/devstack,bigswitch/devstack,inkerra/devstack,affo/devstack,BSJAIN92/OpenStack,bljgaurav/openstack-test,pombredanne/devstack,bq-xiao/devstack,savi-dev/devstack,vsham20/devstack,dirkmueller/devstack,nttmcl/devstack_public,Mahito/devstack,upadhyay-prashant/devstack,TwinkleChawla/devstack,r-mibu/devstack,flavio-fernandes/devstack,virtualopensystems/devstack,parul24/devstack,neerja28/Devstack_GlusterFS,bljgaurav/openstack-test,Yuriy-Leonov/devstack,wenhuizhang/devstack,nati/devstack_public,ozamiatin/devstack,savi-dev/devstack,citrix-openstack-build/devstack,dtroyer/devstack,bswartz/devstack,richliu/devstack,JioCloud/devstack,atulpatil301/devstack,citrix-openstack-build/devstack,eharney/devstack,HPCHub/devstack,varunarya10/devstack,cloudbuilders/devstack,openstack-dev/devstack,LoHChina/devstack,pacinete/devstack,sequenceiq/devstack,olivierlemasle/devstack,dtroyer/devstack,ewindisch/raspi-devstack,Juniper/devstack,CloudServer/devstack,nati/devstack_public,eharney/devstack,samgoon/devstack,mmasaki/devstack,tianweizhang/devstack,group-policy/devstack,ozamiatin/devstack,BSJAIN92/OpenStack,sstrato/devstack,vsham20/devstack,kplus/devstack-moonshot,srics/devstack,wenhuizhang/devstack,jamielennox/devstack,mmasaki/devstack,deepakselvaraj/devstack,pczerkas/devstack,sc68cal/devstack,group-policy/devstack,NaokiMiyata/devstack,liuquansheng47/devstack,LoHChina/devstack,promptworks/devstack,tianweizhang/devstack,nawawi/openstack,rushiagr/devstack,mssumanth/devstack,ewindisch/raspi-devstack,pczerkas/devstack,thomasem/devstack,rushiagr/devstack,armando-migliaccio/devstack,ykaneko/devstack,NaokiMiyata/devstack,noironetworks/devstack,andrewrothstein/devstack,HPCHub/devstack,ykaneko/devstack,mssumanth/devstack,herrsechs/devstack,bswartz/devstack,samgoon/devstack,sc68cal/devstack,neerja28/Devstack_GlusterFS,costingalan/devstack,mc2014/devstack,vishnugonela/devstack,varunarya10/devstack,TwinkleChawla/devstack,andrewrothstein/devstack,kplus/devstack-moonshot