Replace deprecated UPPER_CONSTRAINTS_FILE variable
Replace deprecated UPPER_CONSTRAINTS_FILE variable

UPPER_CONSTRAINTS_FILE is deprecated and TOX_CONSTRAINTS_FILE is
the new environment variable name that replaces it [1].

This allows to use upper-constraints file as more
readable way instead of UPPER_CONSTRAINTS_FILE=<lower-constraints file>.

[1] https://zuul-ci.org/docs/zuul-jobs/python-roles.html#rolevar-tox.tox_constraints_file
[2] https://review.opendev.org/#/c/722814/

Change-Id: Ib92ab839fafc873a5fd09042f35e95bf9c32dc25

openstack/puppet-monasca,openstack/puppet-monasca,openstack/puppet-monasca,openstack/puppet-monasca,openstack/puppet-monasca