Change forward_bridge_interface to MultiStrOpt
Change forward_bridge_interface to MultiStrOpt

The config option specifically mentions it can be set multiple times
but it was accidentally set to a ListOpt instead of a MultiStrOpt.

Change-Id: Ibc4280c4bbdd10655192fb8bb5a810125555eb6d

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