Revert "Allow backup to be run as non-root user (#366)" (#370)

This reverts commit f64aaa6e24.

test/nonroot/docker-compose.yml

@@ -1,33 +0,0 @@
-version: '3'
-
-services:
-  minio:
-    image: minio/minio:RELEASE.2020-08-04T23-10-51Z
-    environment:
-      MINIO_ROOT_USER: test
-      MINIO_ROOT_PASSWORD: test
-      MINIO_ACCESS_KEY: test
-      MINIO_SECRET_KEY: GMusLtUmILge2by+z890kQ
-    entrypoint: /bin/ash -c 'mkdir -p /data/backup && minio server /data'
-    volumes:
-      - ${LOCAL_DIR:-local}:/data
-
-  backup:
-    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
-    user: 1000:1000
-    depends_on:
-      - minio
-    restart: always
-    volumes:
-      - app_data:/backup/app_data:ro
-      - ./01conf.env:/etc/dockervolumebackup/conf.d/01conf.env
-
-  offen:
-    image: offen/offen:latest
-    labels:
-      - docker-volume-backup.stop-during-backup=true
-    volumes:
-      - app_data:/var/opt/offen
-
-volumes:
-  app_data: