refactor and update bind v9.21

bind/Dockerfile

@@ -1,3 +1,4 @@
-FROM debian:buster-slim
-RUN apt update && apt -y upgrade && apt install -y bind9 ipv6calc curl bc && apt clean
-
+FROM bind9-docker
+RUN apk add ipcalc bash
+COPY ./bind/entrypoint.sh /etc/bind/
+ENTRYPOINT "/etc/bind/entrypoint.sh"