Use test container in CI

.gitlab-ci.yml

@@ -9,7 +9,8 @@ test_python:
   services:
     - docker:18.09.7-dind
   script:
-    - make build_test_env test
+    - docker build . -t wccl_test -f src/tests/docker/Dockerfile
+    - docker run --rm -v /tmp/test-out:/test/testdata/out wccl_test
 
 build_image:
   stage: build