libvirt: move setting of clock out into helper method
libvirt: move setting of clock out into helper method

Move clock settings will be added in the future, so it
makes sense to have a separate helper method for all
of them.

Related-bug: #1400315
Change-Id: I1662e2d1e2e729da873c14a0cc307e412c699320

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