ci: make sure to use legacy test runner on EL7

EL7 doesn't have the required dependencies for the newer pytest runner.
Since make check now invokes the pytest runner, ensure that the legacy
runner will be used instead.

.gitlab-ci.yml

@@ -412,14 +412,13 @@ cross-version-config-tests:
 .system_test_legacy: &system_test_legacy
   script:
     - cd bin/tests/system
-    - make -j${TEST_PARALLEL_JOBS:-1} -k check V=1
+    - find . -maxdepth 2 -mindepth 2 -type f -name "tests.sh" | cut -d/ -f2 | xargs -n 1 -P ${TEST_PARALLEL_JOBS:-1} sh legacy.run.sh
     - if git rev-parse > /dev/null 2>&1; then ( ! grep "^I:.*:file.*not removed$" *.log ); fi
     - '( ! grep -F "grep: warning:" *.log )'
   after_script:
     - test -d bind-* && cd bind-*
     - REALSOURCEDIR="$PWD"
     - test -n "${OUT_OF_TREE_WORKSPACE}" && cd "${OUT_OF_TREE_WORKSPACE}"
-    - cat bin/tests/system/test-suite.log
     - find bin/tests/system -name "*dig.*" | xargs grep "error" || true
     - *find_python
     - >