fix pre_block_migration() interaction with libvirt cache
fix pre_block_migration() interaction with libvirt cache

Fixes bug 932179

* nova/virt/libvirt/connection (pre_block_migration):
Don't pass the 'ephemeral_gb' attribute as the size,
since this has the wrong units and is the wrong quantity
to pass anyway.  Also don't check for file existence,
or create the cow image as this is done within _cache_image()

Change-Id: Id723ec8d119dacd4660e88e546e05af417c736fc

phenoxim/nova,raildo/nova,felixma/nova,ruslanloman/nova,joker946/nova,whitepages/nova,alexandrucoman/vbox-nova-driver,klmitch/nova,mikalstill/nova,sridevikoushik31/nova,zzicewind/nova,zzicewind/nova,fajoy/nova,rajalokan/nova,maoy/zknova,virtualopensystems/nova,gooddata/openstack-nova,jianghuaw/nova,devendermishrajio/nova,viggates/nova,gspilio/nova,imsplitbit/nova,maheshp/novatest,imsplitbit/nova,takeshineshiro/nova,petrutlucian94/nova_dev,rahulunair/nova,thomasem/nova,bgxavier/nova,dims/nova,silenceli/nova,sridevikoushik31/openstack,CEG-FYP-OpenStack/scheduler,akash1808/nova,Yusuke1987/openstack_template,ruslanloman/nova,openstack/nova,maheshp/novatest,affo/nova,aristanetworks/arista-ovs-nova,apporc/nova,yosshy/nova,rrader/nova-docker-plugin,alaski/nova,vladikr/nova_drafts,bigswitch/nova,leilihh/nova,projectcalico/calico-nova,adelina-t/nova,shahar-stratoscale/nova,tangfeixiong/nova,double12gzh/nova,CloudServer/nova,saleemjaveds/https-github.com-openstack-nova,zhimin711/nova,blueboxgroup/nova,savi-dev/nova,rajalokan/nova,tanglei528/nova,maelnor/nova,tianweizhang/nova,rahulunair/nova,Metaswitch/calico-nova,ted-gould/nova,CiscoSystems/nova,iuliat/nova,Yuriy-Leonov/nova,berrange/nova,varunarya10/nova_test_latest,mikalstill/nova,saleemjaveds/https-github.com-openstack-nova,citrix-openstack-build/nova,fnordahl/nova,shail2810/nova,NeCTAR-RC/nova,zaina/nova,josephsuh/extra-specs,Yuriy-Leonov/nova,isyippee/nova,ntt-sic/nova,jeffrey4l/nova,badock/nova,Francis-Liu/animated-broccoli,Triv90/Nova,apporc/nova,cyx1231st/nova,alexandrucoman/vbox-nova-driver,sacharya/nova,Francis-Liu/animated-broccoli,adelina-t/nova,eonpatapon/nova,fnordahl/nova,petrutlucian94/nova,SUSE-Cloud/nova,gspilio/nova,devendermishrajio/nova,psiwczak/openstack,Juniper/nova,sileht/deb-openstack-nova,dstroppa/openstack-smartos-nova-grizzly,dstroppa/openstack-smartos-nova-grizzly,josephsuh/extra-specs,DirectXMan12/nova-hacking,rickerc/nova_audit,devendermishrajio/nova_test_latest,eneabio/nova,rickerc/nova_audit,cloudbau/nova,eayunstack/nova,cernops/nova,CiscoSystems/nova,barnsnake351/nova,maoy/zknova,gooddata/openstack-nova,cloudbase/nova-virtualbox,vladikr/nova_drafts,vmturbo/nova,vmturbo/nova,houshengbo/nova_vmware_compute_driver,noironetworks/nova,jianghuaw/nova,redhat-openstack/nova,yrobla/nova,NewpTone/stacklab-nova,tianweizhang/nova,maelnor/nova,usc-isi/extra-specs,luogangyi/bcec-nova,j-carpentier/nova,bgxavier/nova,sacharya/nova,qwefi/nova,jianghuaw/nova,maheshp/novatest,silenceli/nova,citrix-openstack-build/nova,petrutlucian94/nova_dev,gspilio/nova,josephsuh/extra-specs,Brocade-OpenSource/OpenStack-DNRM-Nova,felixma/nova,NewpTone/stacklab-nova,rrader/nova-docker-plugin,CEG-FYP-OpenStack/scheduler,cernops/nova,psiwczak/openstack,Brocade-OpenSource/OpenStack-DNRM-Nova,JioCloud/nova_test_latest,tanglei528/nova,projectcalico/calico-nova,affo/nova,klmitch/nova,kimjaejoong/nova,DirectXMan12/nova-hacking,sridevikoushik31/openstack,NoBodyCam/TftpPxeBootBareMetal,TieWei/nova,Stavitsky/nova,alvarolopez/nova,alaski/nova,mgagne/nova,viggates/nova,alvarolopez/nova,tudorvio/nova,maoy/zknova,Metaswitch/calico-nova,leilihh/novaha,plumgrid/plumgrid-nova,LoHChina/nova,OpenAcademy-OpenStack/nova-scheduler,houshengbo/nova_vmware_compute_driver,JianyuWang/nova,hanlind/nova,hanlind/nova,jianghuaw/nova,devendermishrajio/nova_test_latest,j-carpentier/nova,varunarya10/nova_test_latest,klmitch/nova,eneabio/nova,CCI-MOC/nova,sridevikoushik31/nova,thomasem/nova,jeffrey4l/nova,orbitfp7/nova,belmiromoreira/nova,scripnichenko/nova,qwefi/nova,mmnelemane/nova,Yusuke1987/openstack_template,NeCTAR-RC/nova,leilihh/novaha,noironetworks/nova,rahulunair/nova,cloudbase/nova,hanlind/nova,dims/nova,redhat-openstack/nova,yrobla/nova,sebrandon1/nova,eonpatapon/nova,BeyondTheClouds/nova,mikalstill/nova,devoid/nova,Tehsmash/nova,paulmathews/nova,dawnpower/nova,openstack/nova,openstack/nova,CCI-MOC/nova,gooddata/openstack-nova,watonyweng/nova,Juniper/nova,NewpTone/stacklab-nova,nikesh-mahalka/nova,sridevikoushik31/nova,JioCloud/nova_test_latest,paulmathews/nova,aristanetworks/arista-ovs-nova,raildo/nova,ewindisch/nova,Tehsmash/nova,fajoy/nova,edulramirez/nova,yosshy/nova,cernops/nova,badock/nova,cyx1231st/nova,virtualopensystems/nova,NoBodyCam/TftpPxeBootBareMetal,usc-isi/extra-specs,akash1808/nova_test_latest,eayunstack/nova,paulmathews/nova,dawnpower/nova,devoid/nova,kimjaejoong/nova,LoHChina/nova,sebrandon1/nova,petrutlucian94/nova,angdraug/nova,shahar-stratoscale/nova,eharney/nova,luogangyi/bcec-nova,tudorvio/nova,mahak/nova,sridevikoushik31/nova,Triv90/Nova,MountainWei/nova,eharney/nova,cloudbase/nova-virtualbox,mgagne/nova,mandeepdhami/nova,tealover/nova,belmiromoreira/nova,mmnelemane/nova,zhimin711/nova,shootstar/novatest,berrange/nova,BeyondTheClouds/nova,leilihh/nova,gooddata/openstack-nova,JioCloud/nova,mandeepdhami/nova,isyippee/nova,angdraug/nova,sileht/deb-openstack-nova,dstroppa/openstack-smartos-nova-grizzly,shail2810/nova,barnsnake351/nova,JianyuWang/nova,joker946/nova,NoBodyCam/TftpPxeBootBareMetal,usc-isi/extra-specs,cloudbase/nova,BeyondTheClouds/nova,TwinkleChawla/nova,yrobla/nova,zaina/nova,takeshineshiro/nova,mahak/nova,vmturbo/nova,eneabio/nova,savi-dev/nova,cloudbau/nova,tangfeixiong/nova,SUSE-Cloud/nova,Juniper/nova,bigswitch/nova,phenoxim/nova,shootstar/novatest,savi-dev/nova,rajalokan/nova,psiwczak/openstack,houshengbo/nova_vmware_compute_driver,cloudbase/nova,plumgrid/plumgrid-nova,usc-isi/nova,TwinkleChawla/nova,yatinkumbhare/openstack-nova,whitepages/nova,iuliat/nova,usc-isi/nova,fajoy/nova,watonyweng/nova,akash1808/nova,blueboxgroup/nova,klmitch/nova,CloudServer/nova,TieWei/nova,Juniper/nova,tealover/nova,scripnichenko/nova,ewindisch/nova,MountainWei/nova,rajalokan/nova,mahak/nova,DirectXMan12/nova-hacking,usc-isi/nova,akash1808/nova_test_latest,OpenAcademy-OpenStack/nova-scheduler,sridevikoushik31/openstack,orbitfp7/nova,yatinkumbhare/openstack-nova,Stavitsky/nova,JioCloud/nova,spring-week-topos/nova-week,bclau/nova,Triv90/Nova,sebrandon1/nova,vmturbo/nova,sileht/deb-openstack-nova,bclau/nova,aristanetworks/arista-ovs-nova,nikesh-mahalka/nova,double12gzh/nova,ted-gould/nova,edulramirez/nova,spring-week-topos/nova-week,ntt-sic/nova