Revert "always make upper-constraints available to python jobs"
Revert "always make upper-constraints available to python jobs"

This is happening in non-change-pipeline jobs where zuul-cloner is
not yet appropriate to be used (for example, it broke generating
release tarballs with errors like "INFO:zuul.Cloner:upstream repo is
missing branch refs/tags/2015.1.3" and then falling back on the
master branch tip).

This reverts commit 405ed43c216847faca6bb99c1499e904b6732229.

Change-Id: I7a85f7bdf661efa07e6e8627ec84ffcb52d01c3e

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