Dockerfile: Provide backup of district/static:nonroot image. radondb#287

Dockerfile

@@ -27,7 +27,7 @@ RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -o manager cmd/manager/mai
 # Refer to https://github.com/GoogleContainerTools/distroless for more details
 FROM gcr.io/distroless/static:nonroot
 # If you make a image manually, the cn environment may not be able to access .io, you can switch to the following path
-# FROM gcr.azk8s.cn/distroless/static:nonroot
+# FROM radondb/distroless:nonroot
 WORKDIR /
 COPY --from=builder /workspace/manager .
 USER 65532:65532