Remove unnecessary use of LoopingCall in nova/virt/xenapi/vm_utils.py
Remove unnecessary use of LoopingCall in nova/virt/xenapi/vm_utils.py

The code synchronously blocks waiting on the LoopingCall to finish
anyway and the use of a maximum of number of attempts ends up being
awkwardly fit in.

Also, remove an out-of-date comment about future use of LoopingCall

Change-Id: Ife397e171f28fff5e73c70e6957cecdd09a42d68

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