doc: document AWS_VPC_K8S_CNI_LOGLEVEL for cni-metric-helper helm chart

[csantanapr]

What type of PR is this?

Document the variable AWS_VPC_K8S_CNI_LOGLEVEL and set the default value to INFO

Add one of the following:
cleanup
documentation

Which issue does this PR fix:
Fixes #2207

Document environment variable `AWS_VPC_K8S_CNI_LOGLEVEL` for cni-metric-helper

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[jdn5126]

@csantanapr thank you for the contribution! This change looks good to me, though we should also increment the chart revision. @jayanthvn are you ok with this default changing?

[jdn5126]

@csantanapr thank you for the contribution! This change looks good to me, though we should also increment the chart revision. @jayanthvn are you ok with this default changing?

Discussed offline and changing this log default in the chart is fine. @csantanapr I can merge this after you increment the Chart version: https://github.com/aws/amazon-vpc-cni-k8s/blob/master/charts/cni-metrics-helper/Chart.yaml#L3

[jayanthvn]

@csantanapr thank you for the contribution! This change looks good to me, though we should also increment the chart revision. @jayanthvn are you ok with this default changing?

Discussed offline and changing this log default in the chart is fine. @csantanapr I can merge this after you increment the Chart version: https://github.com/aws/amazon-vpc-cni-k8s/blob/master/charts/cni-metrics-helper/Chart.yaml#L3

@jdn5126 CNI has default as DEBUG, any specific reason to make it INFO?

[jdn5126]

@csantanapr thank you for the contribution! This change looks good to me, though we should also increment the chart revision. @jayanthvn are you ok with this default changing?

Discussed offline and changing this log default in the chart is fine. @csantanapr I can merge this after you increment the Chart version: https://github.com/aws/amazon-vpc-cni-k8s/blob/master/charts/cni-metrics-helper/Chart.yaml#L3

@jdn5126 CNI has default as DEBUG, any specific reason to make it INFO?

For CNI Metrics Helper, I think INFO is a reasonable default, as some logs like https://github.com/aws/amazon-vpc-cni-k8s/blob/master/cmd/cni-metrics-helper/metrics/cni_metrics.go#L196 are extremely verbose, adding to ops cost as mentioned in #2207 . This is a helpful log if we need to debug what is sent to CloudWatch, though.