Resolve circular dependency when tracking dependencies.
Resolve circular dependency when tracking dependencies.

When TRACK_DEPENDS=True, there is a circular dependency wherein virtualenv is
used to install virtualenv before a virtualenv has been established.
TRACK_DEPENDS does not work in any use case without this fix.

Change-Id: I7a6652ba091cb95dac3871b6c71edcd762a7be62
Closes-Bug: 1208867

openstack-dev/devstack,andrewrothstein/devstack,herrsechs/devstack,richliu/devstack,prithivm/branch01,thomasem/devstack,samgoon/devstack,mssumanth/devstack,virtualopensystems/devstack,sc68cal/devstack,HPCHub/devstack,BSJAIN92/OpenStack,openstack-dev/devstack,TwinkleChawla/devstack,BSJAIN92/OpenStack,CloudServer/devstack,ozamiatin/devstack,kplus/devstack-moonshot,LoHChina/devstack,avvocatodemarchis/devstack,bq-xiao/devstack,eshnil2000/devstack,upadhyay-prashant/devstack,bljgaurav/openstack-test,wenhuizhang/devstack,flavio-fernandes/devstack,dirkmueller/devstack,varunarya10/devstack,sc68cal/devstack,nuxeh/devstack,tianweizhang/devstack,eharney/devstack,atulpatil301/devstack,neerja28/Devstack_GlusterFS,j4/devstack,sequenceiq/devstack,costingalan/devstack,vsham20/devstack,prithivm/branch01,affo/devstack,bswartz/devstack,parul24/devstack,affo/devstack,nawawi/openstack,NaokiMiyata/devstack,pacinete/devstack,LoHChina/devstack,parul24/devstack,liuquansheng47/devstack,avvocatodemarchis/devstack,pombredanne/devstack,dtroyer/devstack,mmasaki/devstack,liuquansheng47/devstack,olivierlemasle/devstack,HPCHub/devstack,vishnugonela/devstack,nuxeh/devstack,group-policy/devstack,bswartz/devstack,Mahito/devstack,bljgaurav/openstack-test,NaokiMiyata/devstack,dtroyer/devstack,richliu/devstack,vishnugonela/devstack,eharney/devstack,TwinkleChawla/devstack,thomasem/devstack,noironetworks/devstack,neerja28/Devstack_GlusterFS,mc2014/devstack,upadhyay-prashant/devstack,pczerkas/devstack,bq-xiao/devstack,costingalan/devstack,promptworks/devstack,pacinete/devstack,bigswitch/devstack,rushiagr/devstack,bigswitch/devstack,flavio-fernandes/devstack,sequenceiq/devstack,nawawi/openstack,mmasaki/devstack,rushiagr/devstack,mc2014/devstack,Mahito/devstack,wenhuizhang/devstack,dirkmueller/devstack,pombredanne/devstack,CloudServer/devstack,samgoon/devstack,olivierlemasle/devstack,tianweizhang/devstack,varunarya10/devstack,pczerkas/devstack,ozamiatin/devstack,mssumanth/devstack,noironetworks/devstack,herrsechs/devstack,kplus/devstack-moonshot,andrewrothstein/devstack,atulpatil301/devstack,j4/devstack,vsham20/devstack,group-policy/devstack,promptworks/devstack