do not hang when running docker

Author: 3nids

.ci/travis/docker_image/script.sh

@@ -34,8 +34,9 @@ docker login -u="$DOCKER_USERNAME" -p="$DOCKER_PASSWORD"
 docker push "qgis/qgis:${DOCKER_TAG}"
 echo "Copy build cache from Docker container to Travis cache directory"
 rm -rf "${CCACHE_DIR:?}/"*
-docker run --name qgis_container qgis/qgis:${DOCKER_TAG}
+docker run --name qgis_container qgis/qgis:${DOCKER_TAG} /bin/true
 docker cp qgis_container:/usr/src/QGIS/.ccache_image_build ${CCACHE_DIR}
+docker rm qgis_container
 popd
 echo "Trigger build of PyQGIS Documentation"
 body='{