Change install script to use git.o.o
Change install script to use git.o.o

These mirrors have a better uptime than github.com and are under the
direct control of OpenStack's infra team.

Change-Id: I3fdddc5c6c3be3fe1b5f7b071401e66607bca5e7

eayunstack/rally,yeming233/rally,gluke77/rally,group-policy/rally,openstack/rally,vganapath/rally,eayunstack/rally,vganapath/rally,openstack/rally,amit0701/rally,group-policy/rally,vganapath/rally,openstack/rally,amit0701/rally,eayunstack/rally,openstack/rally,gluke77/rally,group-policy/rally,yeming233/rally,gluke77/rally,amit0701/rally,eonpatapon/rally,gluke77/rally,vganapath/rally,eonpatapon/rally