pass environment variables of proxy to tox
pass environment variables of proxy to tox

When a development environment is under a proxy, tox is failed even if
environment variables of the proxy are set.

This patch fix this problem.

Change-Id: If0bc42891a0714cc9b37b9c211388db20555ea7e

klmitch/nova,sebrandon1/nova,rahulunair/nova,MountainWei/nova,apporc/nova,yatinkumbhare/openstack-nova,jeffrey4l/nova,jianghuaw/nova,MountainWei/nova,klmitch/nova,watonyweng/nova,eonpatapon/nova,mikalstill/nova,CCI-MOC/nova,cloudbase/nova,iuliat/nova,openstack/nova,tudorvio/nova,mahak/nova,j-carpentier/nova,whitepages/nova,rajalokan/nova,hanlind/nova,BeyondTheClouds/nova,shail2810/nova,yatinkumbhare/openstack-nova,scripnichenko/nova,rajalokan/nova,JioCloud/nova_test_latest,alaski/nova,vmturbo/nova,jianghuaw/nova,rajalokan/nova,raildo/nova,BeyondTheClouds/nova,openstack/nova,tudorvio/nova,scripnichenko/nova,kimjaejoong/nova,mahak/nova,devendermishrajio/nova,felixma/nova,ted-gould/nova,zaina/nova,jeffrey4l/nova,zzicewind/nova,vmturbo/nova,mikalstill/nova,dims/nova,TwinkleChawla/nova,Juniper/nova,sebrandon1/nova,CEG-FYP-OpenStack/scheduler,Stavitsky/nova,CloudServer/nova,tangfeixiong/nova,hanlind/nova,TwinkleChawla/nova,Stavitsky/nova,watonyweng/nova,CCI-MOC/nova,Juniper/nova,j-carpentier/nova,mahak/nova,isyippee/nova,takeshineshiro/nova,phenoxim/nova,takeshineshiro/nova,fnordahl/nova,felixma/nova,mikalstill/nova,ruslanloman/nova,ruslanloman/nova,devendermishrajio/nova_test_latest,gooddata/openstack-nova,Juniper/nova,cernops/nova,cyx1231st/nova,apporc/nova,cernops/nova,devendermishrajio/nova_test_latest,varunarya10/nova_test_latest,jianghuaw/nova,fnordahl/nova,belmiromoreira/nova,klmitch/nova,double12gzh/nova,mmnelemane/nova,gooddata/openstack-nova,BeyondTheClouds/nova,edulramirez/nova,jianghuaw/nova,akash1808/nova_test_latest,zhimin711/nova,mmnelemane/nova,zaina/nova,barnsnake351/nova,gooddata/openstack-nova,Tehsmash/nova,NeCTAR-RC/nova,LoHChina/nova,gooddata/openstack-nova,akash1808/nova_test_latest,mandeepdhami/nova,JianyuWang/nova,klmitch/nova,zzicewind/nova,cloudbase/nova,whitepages/nova,yosshy/nova,phenoxim/nova,cloudbase/nova,dims/nova,rajalokan/nova,devendermishrajio/nova,LoHChina/nova,rahulunair/nova,openstack/nova,iuliat/nova,zhimin711/nova,noironetworks/nova,isyippee/nova,eonpatapon/nova,belmiromoreira/nova,cernops/nova,Francis-Liu/animated-broccoli,nikesh-mahalka/nova,nikesh-mahalka/nova,bigswitch/nova,vmturbo/nova,JianyuWang/nova,JioCloud/nova_test_latest,double12gzh/nova,mandeepdhami/nova,shail2810/nova,Juniper/nova,rahulunair/nova,edulramirez/nova,sebrandon1/nova,ted-gould/nova,cyx1231st/nova,noironetworks/nova,varunarya10/nova_test_latest,Francis-Liu/animated-broccoli,raildo/nova,yosshy/nova,tangfeixiong/nova,CloudServer/nova,alaski/nova,NeCTAR-RC/nova,vmturbo/nova,barnsnake351/nova,CEG-FYP-OpenStack/scheduler,hanlind/nova,bigswitch/nova,Tehsmash/nova,kimjaejoong/nova