Tweak CI device settings

.gitlab-ci.yml

 Python 2.7 AMD CPU:
   script:
   - py_version=2.7
-  - cl_dev=amd_pu
+  - export PYOPENCL_TEST=amd:pu
   - EXTRA_INSTALL="numpy mako"
   - curl -L -O -k https://gitlab.tiker.net/inducer/ci-support/raw/master/build-and-test-py-project.sh
   - ". ./build-and-test-py-project.sh"