Generate an IPv6 address when PUBLIC_BRIDGE does not have one
Generate an IPv6 address when PUBLIC_BRIDGE does not have one

Closes-Bug: #1400823
Change-Id: Ic79fd003aea2af7b258397ec2cdfd70c8568743c

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