Fix vol_usage_update() DB API tests.
Fix vol_usage_update() DB API tests.

vol_usage_update() method filters VolumeCache instances by
value of 'volume_id' column, which is of type varchar(36).
The problem is that a caller can pass 'volume_id' argument
as an integer value. On PostgreSQL this leads to the following
error when the SQL query is executed:

    ProgrammingError: (ProgrammingError) operator does not exist:
                      character varying = integer
    LINE 3: WHERE volume_usage_cache.volume_id = 1

Blueprint: db-api-tests-on-all-backends

Change-Id: I5ff1fa36d5494a15ec8b3bc1bfa9bb1c1af9fe97

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