xenapi: attach root disk during rescue before boot
xenapi: attach root disk during rescue before boot

Fixes bug 1037729

The xenapi driver attaches the root disk after the rescue instance has
booted. However, hotplugging block devices is only supported on images
that use PV drivers. Attaching the disk before the rescue instance boots
will allow rescue to work on instances that don't use PV drivers.

Change-Id: I187762e4f1ea921d81afd40fcbde0b93d7d3cbc1

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