ovs_base: Fix debug-agent config for Q_USE_PROVIDERNET_FOR_PUBLIC=True
ovs_base: Fix debug-agent config for Q_USE_PROVIDERNET_FOR_PUBLIC=True

Set up external_network_bridge correctly for the case
of Q_USE_PROVIDERNET_FOR_PUBLIC=True.

This is an oversight in commit 6a633fd024347aade777ecd6545fa3efde5a959c.

Closes-Bug: #1394826
Change-Id: I33f0fe15bafb7071d8a09899d636471f49031606

varunarya10/devstack,group-policy/devstack,affo/devstack,TwinkleChawla/devstack,sc68cal/devstack,upadhyay-prashant/devstack,HPCHub/devstack,andrewrothstein/devstack,mssumanth/devstack,promptworks/devstack,ozamiatin/devstack,bq-xiao/devstack,affo/devstack,bswartz/devstack,wenhuizhang/devstack,neerja28/Devstack_GlusterFS,bigswitch/devstack,vsham20/devstack,nawawi/openstack,pczerkas/devstack,andrewrothstein/devstack,HPCHub/devstack,kplus/devstack-moonshot,samgoon/devstack,NaokiMiyata/devstack,LoHChina/devstack,dtroyer/devstack,BSJAIN92/OpenStack,liuquansheng47/devstack,bljgaurav/openstack-test,parul24/devstack,sequenceiq/devstack,eharney/devstack,olivierlemasle/devstack,BSJAIN92/OpenStack,costingalan/devstack,rushiagr/devstack,avvocatodemarchis/devstack,pombredanne/devstack,mssumanth/devstack,rushiagr/devstack,promptworks/devstack,bq-xiao/devstack,TwinkleChawla/devstack,dirkmueller/devstack,vishnugonela/devstack,parul24/devstack,prithivm/branch01,group-policy/devstack,Mahito/devstack,pacinete/devstack,flavio-fernandes/devstack,liuquansheng47/devstack,costingalan/devstack,bswartz/devstack,eharney/devstack,openstack-dev/devstack,prithivm/branch01,openstack-dev/devstack,upadhyay-prashant/devstack,samgoon/devstack,bigswitch/devstack,noironetworks/devstack,j4/devstack,pacinete/devstack,neerja28/Devstack_GlusterFS,j4/devstack,CloudServer/devstack,sequenceiq/devstack,varunarya10/devstack,NaokiMiyata/devstack,CloudServer/devstack,atulpatil301/devstack,mmasaki/devstack,mc2014/devstack,pczerkas/devstack,noironetworks/devstack,thomasem/devstack,richliu/devstack,atulpatil301/devstack,nuxeh/devstack,nuxeh/devstack,pombredanne/devstack,avvocatodemarchis/devstack,dirkmueller/devstack,kplus/devstack-moonshot,herrsechs/devstack,wenhuizhang/devstack,ozamiatin/devstack,mmasaki/devstack,richliu/devstack,herrsechs/devstack,LoHChina/devstack,mc2014/devstack,Mahito/devstack,vsham20/devstack,bljgaurav/openstack-test,flavio-fernandes/devstack,olivierlemasle/devstack,sc68cal/devstack,dtroyer/devstack,vishnugonela/devstack,nawawi/openstack,thomasem/devstack