Make sure that nginx becomes PID1

[refs #39f59d255af4]

Author: jfahrer

nginx/Dockerfile

@@ -3,4 +3,5 @@ FROM debian:buster-slim
 RUN apt-get update
 RUN apt-get install -y nginx
 
-CMD nginx -g 'daemon off;'
+CMD ["/usr/sbin/nginx", "-g", "daemon off;"]
+