xenapi: reorder volume_utils
xenapi: reorder volume_utils

Grouping related functions together. Renamed _create_pbd to show it is
not called outside volume_utils.

Change-Id: If6106a81d58e059e2e683ad0556d4225a9b894e2

klmitch/nova,barnsnake351/nova,akash1808/nova_test_latest,mgagne/nova,zhimin711/nova,JioCloud/nova_test_latest,klmitch/nova,yosshy/nova,Juniper/nova,BeyondTheClouds/nova,Stavitsky/nova,CEG-FYP-OpenStack/scheduler,ruslanloman/nova,jeffrey4l/nova,tangfeixiong/nova,JioCloud/nova,saleemjaveds/https-github.com-openstack-nova,ted-gould/nova,blueboxgroup/nova,redhat-openstack/nova,thomasem/nova,akash1808/nova,mikalstill/nova,noironetworks/nova,rahulunair/nova,zaina/nova,felixma/nova,scripnichenko/nova,cloudbase/nova,iuliat/nova,angdraug/nova,tianweizhang/nova,rajalokan/nova,joker946/nova,dims/nova,whitepages/nova,cyx1231st/nova,zaina/nova,shail2810/nova,iuliat/nova,mikalstill/nova,Juniper/nova,hanlind/nova,yatinkumbhare/openstack-nova,berrange/nova,vladikr/nova_drafts,LoHChina/nova,gooddata/openstack-nova,ted-gould/nova,devendermishrajio/nova_test_latest,Yusuke1987/openstack_template,alvarolopez/nova,j-carpentier/nova,alvarolopez/nova,mikalstill/nova,JioCloud/nova_test_latest,j-carpentier/nova,hanlind/nova,raildo/nova,berrange/nova,redhat-openstack/nova,zhimin711/nova,apporc/nova,vmturbo/nova,devendermishrajio/nova_test_latest,mmnelemane/nova,badock/nova,MountainWei/nova,eayunstack/nova,TwinkleChawla/nova,nikesh-mahalka/nova,mgagne/nova,silenceli/nova,gooddata/openstack-nova,watonyweng/nova,Stavitsky/nova,BeyondTheClouds/nova,sebrandon1/nova,JianyuWang/nova,belmiromoreira/nova,bigswitch/nova,vladikr/nova_drafts,fnordahl/nova,phenoxim/nova,jianghuaw/nova,rajalokan/nova,takeshineshiro/nova,silenceli/nova,cloudbase/nova,Yusuke1987/openstack_template,apporc/nova,devendermishrajio/nova,kimjaejoong/nova,belmiromoreira/nova,affo/nova,virtualopensystems/nova,shail2810/nova,klmitch/nova,double12gzh/nova,alaski/nova,raildo/nova,LoHChina/nova,rahulunair/nova,affo/nova,BeyondTheClouds/nova,takeshineshiro/nova,Metaswitch/calico-nova,hanlind/nova,jianghuaw/nova,edulramirez/nova,CloudServer/nova,dawnpower/nova,rajalokan/nova,maelnor/nova,fnordahl/nova,bigswitch/nova,jeffrey4l/nova,jianghuaw/nova,TwinkleChawla/nova,blueboxgroup/nova,Francis-Liu/animated-broccoli,mahak/nova,maelnor/nova,scripnichenko/nova,tudorvio/nova,sebrandon1/nova,openstack/nova,cernops/nova,openstack/nova,varunarya10/nova_test_latest,yosshy/nova,akash1808/nova_test_latest,varunarya10/nova_test_latest,klmitch/nova,gooddata/openstack-nova,vmturbo/nova,akash1808/nova,tealover/nova,CCI-MOC/nova,kimjaejoong/nova,double12gzh/nova,petrutlucian94/nova,mandeepdhami/nova,barnsnake351/nova,vmturbo/nova,zzicewind/nova,joker946/nova,mandeepdhami/nova,cloudbase/nova,Metaswitch/calico-nova,alexandrucoman/vbox-nova-driver,Francis-Liu/animated-broccoli,alexandrucoman/vbox-nova-driver,projectcalico/calico-nova,cloudbase/nova-virtualbox,virtualopensystems/nova,cloudbase/nova-virtualbox,sebrandon1/nova,eayunstack/nova,Tehsmash/nova,cyx1231st/nova,alaski/nova,dawnpower/nova,rajalokan/nova,devendermishrajio/nova,JianyuWang/nova,badock/nova,nikesh-mahalka/nova,petrutlucian94/nova,bgxavier/nova,Tehsmash/nova,tealover/nova,tudorvio/nova,MountainWei/nova,viggates/nova,vmturbo/nova,NeCTAR-RC/nova,orbitfp7/nova,dims/nova,Juniper/nova,adelina-t/nova,tangfeixiong/nova,ruslanloman/nova,yatinkumbhare/openstack-nova,isyippee/nova,saleemjaveds/https-github.com-openstack-nova,edulramirez/nova,felixma/nova,projectcalico/calico-nova,phenoxim/nova,zzicewind/nova,tianweizhang/nova,gooddata/openstack-nova,eonpatapon/nova,noironetworks/nova,cernops/nova,jianghuaw/nova,orbitfp7/nova,bgxavier/nova,adelina-t/nova,viggates/nova,eonpatapon/nova,whitepages/nova,mahak/nova,rahulunair/nova,JioCloud/nova,CCI-MOC/nova,openstack/nova,Juniper/nova,mahak/nova,isyippee/nova,NeCTAR-RC/nova,thomasem/nova,CloudServer/nova,angdraug/nova,mmnelemane/nova,CEG-FYP-OpenStack/scheduler,watonyweng/nova,cernops/nova