fix(openshift): fix remote write proxy - use unprivileged NGINX

[kasia-kujawa]

ref:

• https://github.com/nginxinc/docker-nginx-unprivileged
• https://hub.docker.com/r/nginxinc/nginx-unprivileged

NGINX Unprivileged Docker Image is owned and maintained by NGINX on both GitHub and Docker Hub, see nginxinc/docker-nginx-unprivileged#19 (comment)

Some details about Nginx on OpenShift can be found here: https://torstenwalter.de/openshift/nginx/2017/08/04/nginx-on-openshift.html

With public.ecr.aws/nginx/nginx:1.21-alpine image following issue occurs on OpenShift 4.10:

% kubectl logs -n sumologic collection-sumologic-remote-write-proxy-5bb47649df-wv2dv  -p
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: can not modify /etc/nginx/conf.d/default.conf (read-only file system?)
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
30-tune-worker-processes.sh: error: can not modify /etc/nginx/nginx.conf (read-only file system?)
/docker-entrypoint.sh: Configuration complete; ready for start up
2022/09/06 15:18:06 [warn] 1#1: the "user" directive makes sense only if the master process runs with super-user privileges, ignored in /etc/nginx/nginx.conf:2
nginx: [warn] the "user" directive makes sense only if the master process runs with super-user privileges, ignored in /etc/nginx/nginx.conf:2
2022/09/06 15:18:06 [emerg] 1#1: mkdir() "/var/cache/nginx/client_temp" failed (13: Permission denied)
nginx: [emerg] mkdir() "/var/cache/nginx/client_temp" failed (13: Permission denied)

kubectl get pods -n sumologic  | grep remote
collection-sumologic-remote-write-proxy-5bb47649df-68vcl     0/1     CrashLoopBackOff   9 (76s ago)   22m
collection-sumologic-remote-write-proxy-5bb47649df-gmlfg     0/1     CrashLoopBackOff   9 (69s ago)   22m
collection-sumologic-remote-write-proxy-5bb47649df-wv2dv     0/1     CrashLoopBackOff   9 (81s ago)   22m

[perk-sumo]

Approve pending one comment about using Docker Hub