made sure the module command is available when running /ci/test_iprcluster.py

this should fix the continuous integration stage('testing (tests that only work on ipr cluster nodes)')

work related to [https://bugzilla.ipr.univ-rennes.fr/show_bug.cgi?id=3958]

ci/ipr.jenkins

@@ -30,6 +30,7 @@ pipeline {
             steps {
                 sh """#!/bin/bash
                 set -o errexit
+                source /etc/profile.d/modules.sh
                 source ${IPRBENCH_VENV_PATH}/bin/activate &&
                 python -m unittest ./ci/test_iprcluster.py
                 """