use a non-root user (#1009) (#1012)

Co-authored-by: Akshay Gupta <[email protected]>

Author: 3quanfeng

dockerfiles/deploy.Dockerfile

@@ -1,6 +1,9 @@
 FROM ubuntu:16.04
 RUN apt-get update
 RUN apt-get install -y ca-certificates openssl
+RUN useradd appgw-ingress-user
 ADD bin/appgw-ingress /
+RUN chown appgw-ingress-user /appgw-ingress
+USER appgw-ingress-user
 RUN chmod +x /appgw-ingress
 CMD ["/appgw-ingress"]