Fix error when tests are being run on partially downloaded data

docker/test/stateful_with_coverage/Dockerfile

-# docker build -t yandex/clickhouse-stateful-test .
+# docker build -t yandex/clickhouse-stateful-test-with-coverage .
 FROM yandex/clickhouse-stateless-test
 
 RUN echo "deb [trusted=yes] http://apt.llvm.org/bionic/ llvm-toolchain-bionic-9 main" >> /etc/apt/sources.list

docker/test/stateful_with_coverage/run.sh

@@ -71,7 +71,11 @@ start_clickhouse
 
 sleep 5
 
-/s3downloader --dataset-names $DATASETS
+if ! /s3downloader --dataset-names $DATASETS; then
+    echo "Cannot download datatsets"
+    exit 1
+fi
+
 
 chmod 777 -R /var/lib/clickhouse