Set ZUUL_REF in constraints proposal job
Set ZUUL_REF in constraints proposal job

The propose_updates.sh script wants to use ZUUL_REF not ZUUL_BRANCH,
so adjust the propose-requirements-constraints{branch-designator}
job-template to pass the correct environment variable.

Change-Id: I831c3c9d256e81f0fc2d00f8f192cbe0b2c82e69

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