Fix DB migration 254 by adding missing unittest
Fix DB migration 254 by adding missing unittest

By merging https://review.openstack.org/#/c/114286/23, a new db migration
was added but the unittest was missing.

Change-Id: I32e2455fd5efb2aad52d9a4d7666783c0e613e75

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