Implement retry logic on downloader

[Shunpoco]

Describe your changes

A downloader needs a retry logic for curl, because sometimes network trouble happens.

This PR does:

• Add a retry logic in the downloader shell script. The number of retry and sleep duration between iteration are configurable
• Modify helm chart to add a ConfigMap for setting those variables on downloader container
• Modify Reconciler code to add the ConfigMap if it is specified
• Add a verification step for a ConfigMap from helm chart to actual installer pod

Issue ticket number and link

#591

Checklist before requesting a review

• I have performed a self-review of my code
• If it is a core feature, I have added thorough tests.
• I tested the changes with the following distributions:
  • Kind
  • MiniKube
  • MicroK8s
  • Rancher RKE2
  • Azure AKS
  • GCP GKE (Ubuntu nodes)
  • AWS EKS (AmazonLinux2 nodes)
  • AWS EKS (Ubuntu nodes)
  • Digital Ocean Kubernetes

[vdice]

Hi @Shunpoco, sorry for the delay in reviewing. This looks really good. I had one thought around simplifying the configuration such that the explicit enabled field is no longer needed. What do you think?

[vdice]

What do you think about removing the enabled field and commenting this sample configuration out? Then, in the deployment template (and any others), we can just use: {{- if .Values.rcm.shimDownloaderConfig }}

Maybe something like:

# shimDownloaderConfig generates a ConfigMap which sets a downloader container's variables. Since those variables have defaults, you don't need to enable it unless you want to customize them.
# shimDownloaderConfig:
#   configMapName: shim-downloader-config
#   content:
#     numRetry: 3
#     sleepDuration: 2

When the user/operator would like to supply different values, they can uncomment and adjust as needed.

[Shunpoco]

Sure, e71016b addressed it.