Lazy load CONF.quota_driver.
Lazy load CONF.quota_driver.

nova.quota is imported before config options are parsed and it looks at
CONF.quota_driver on module-load.  This changes it so we look at
CONF.quota_driver post-module-load.

Fixes bug 1154371

Change-Id: Ia2e63a7aeab2234be683ff507e7856d46601a9a8

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