Fix oslo master jobs failures - missing upper constraints
Fix oslo master jobs failures - missing upper constraints

Looks like there were changes in the CI system which we
need to catch up with:
http://logs.openstack.org/periodic/periodic-nova-py27-with-oslo-master/bc1a2b8/console.html#_2016-03-10_06_04_18_695

the failure is because UPPER_CONSTRAINTS_FILE is
set in run-tox.sh and we need to switch to
zuul-git-branch-prep-upper-constraints so that
the upper-constaints.txt is fetched.

Change-Id: I8a8b4a7da838c62be6b42500b2167d63a553035e

noorul/os-project-config,openstack-infra/project-config,Tesora/tesora-project-config,openstack-infra/project-config,dongwenjuan/project-config,Tesora/tesora-project-config,noorul/os-project-config,dongwenjuan/project-config