Add defaults for yum proxy variables
Add defaults for yum proxy variables

Without these defaults, sourcing functions-common with -u turned on
(as say ./tools/build_wheels.sh does) will bail out with unset
variable errors.  Also fix up quoting, and add no_proxy for zypper run

Change-Id: Ideb441634243c1c5ce7db3a375c2d98617e9d1dc

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