Don't setup swift3 if it's not being used.
Don't setup swift3 if it's not being used.

"setup_develop" was still being called for swift3, even if it's
not in enabled services.  This wraps that call in an
"is_service_enbled" conditional so that stack.sh doesn't attempt
to set it up if it's not enabled.

- Fixes bug 1021150.

Change-Id: I26ed1a1e73eee24da78580eda3b13e5d3eb65361

samgoon/devstack,bq-xiao/devstack,flavio-fernandes/devstack,CiscoSystems/devstack,kplus/devstack-moonshot,dtroyer/devstack,liuquansheng47/devstack,pombredanne/devstack,citrix-openstack-build/devstack,citrix-openstack-build/devstack,vsham20/devstack,richliu/devstack,parul24/devstack,nttmcl/devstack_public,NaokiMiyata/devstack,eshnil2000/devstack,olivierlemasle/devstack,ozamiatin/devstack,BSJAIN92/OpenStack,virtualopensystems/devstack,varunarya10/devstack,r-mibu/devstack,ewindisch/raspi-devstack,BSJAIN92/OpenStack,Millnert/contrail-devstack,bljgaurav/openstack-test,thomasem/devstack,neerja28/Devstack_GlusterFS,inkerra/devstack,ewindisch/raspi-devstack,wenhuizhang/devstack,bswartz/devstack,rushiagr/devstack,affo/devstack,deepakselvaraj/devstack,noironetworks/devstack,dirkmueller/devstack,JioCloud/devstack,sstrato/devstack,group-policy/devstack,pombredanne/devstack,innodee/openstackk,HPCHub/devstack,rushiagr/devstack,dtroyer/devstack,nawawi/openstack,upadhyay-prashant/devstack,j4/devstack,TwinkleChawla/devstack,williamthegrey/devstack,nati/devstack_public,atulpatil301/devstack,avvocatodemarchis/devstack,bljgaurav/openstack-test,dirkmueller/devstack,upadhyay-prashant/devstack,mssumanth/devstack,pacinete/devstack,tianweizhang/devstack,mc2014/devstack,promptworks/devstack,promptworks/devstack,tianweizhang/devstack,j4/devstack,sc68cal/devstack,TwinkleChawla/devstack,bq-xiao/devstack,thomasem/devstack,mmasaki/devstack,vishnugonela/devstack,sequenceiq/devstack,Mahito/devstack,prithivm/branch01,andrewrothstein/devstack,nawawi/openstack,srics/devstack,nuxeh/devstack,varunarya10/devstack,LoHChina/devstack,vsham20/devstack,openstack-dev/devstack,ykaneko/devstack,shootstar/devstacktest,Juniper/devstack,pacinete/devstack,HPCHub/devstack,samgoon/devstack,pczerkas/devstack,flavio-fernandes/devstack,andrewrothstein/devstack,eharney/devstack,Mahito/devstack,NaokiMiyata/devstack,herrsechs/devstack,wenhuizhang/devstack,nuxeh/devstack,bswartz/devstack,bigswitch/devstack,mmasaki/devstack,prithivm/branch01,bigswitch/devstack,nati/devstack_public,noironetworks/devstack,LoHChina/devstack,atulpatil301/devstack,cloudbuilders/devstack,mssumanth/devstack,neerja28/Devstack_GlusterFS,sequenceiq/devstack,mc2014/devstack,pczerkas/devstack,CloudServer/devstack,parul24/devstack,savi-dev/devstack,Yuriy-Leonov/devstack,richliu/devstack,ykaneko/devstack,r-mibu/devstack,eharney/devstack,vishnugonela/devstack,affo/devstack,nttmcl/devstack_public,olivierlemasle/devstack,armando-migliaccio/devstack,openstack-dev/devstack,jamielennox/devstack,cloudbuilders/devstack,sc68cal/devstack,ozamiatin/devstack,herrsechs/devstack,costingalan/devstack,costingalan/devstack,kplus/devstack-moonshot,yamt/devstack,group-policy/devstack,liuquansheng47/devstack,savi-dev/devstack,avvocatodemarchis/devstack,CloudServer/devstack