ci(e2e): pin gpu job container engine

Signed-off-by: Evan Lezar <elezar@nvidia.com>

Author: elezar

.github/workflows/e2e-gpu-test.yaml

@@ -48,6 +48,7 @@ jobs:
       OPENSHELL_REGISTRY_NAMESPACE: nvidia/openshell
       OPENSHELL_REGISTRY_USERNAME: ${{ github.actor }}
       OPENSHELL_REGISTRY_PASSWORD: ${{ secrets.GITHUB_TOKEN }}
+      CONTAINER_ENGINE: docker
       OPENSHELL_E2E_DOCKER_GPU: "1"
       # NVIDIA-managed Ubuntu base used as the GPU probe target: it has the
       # filesystem layout CDI injection expects (ldconfig, populated /usr/bin)