Set IP_VERSION default value to 4+6
Set IP_VERSION default value to 4+6

This is actually the default value since 645114b

Change-Id: Ib6603b4f6ea0b4079f9a4ea46e723ecbb2ea371d

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