Stop using LoopingCall in nova.virt.xenapi_conn:wait_for_task()
Stop using LoopingCall in nova.virt.xenapi_conn:wait_for_task()

The use of utils.LoopingCall is unnecessary since code waits immediately
for the LoopingCall to finish. This results in code that is more
complicated than necessary, but also it creates an extra greenthread
that ends up obfuscating stack trace in case of exceptions.

Change-Id: Iaf0909a4f2307e8657e7baa15cb5a7852ba6feca

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