fix(kube_pod_tolerations): deduplicate tolerations before creating metric

[RiRa12621]

What this PR does / why we need it:
duplicate metrics currently create warnings in the logs of prometheus. Tolerations can be duplicated and kube-api doesn't want to change that behavior, hence we have to deduplicate here

How does this change affect the cardinality of KSM: (increases, decreases or does not change cardinality)
does not change cardinality

Which issue(s) this PR fixes
Fixes #2390

[k8s-ci-robot]

This issue is currently awaiting triage.

If kube-state-metrics contributors determine this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: RiRa12621
Once this PR has been reviewed and has the lgtm label, please assign dgrisonnet for approval. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Welcome @RiRa12621!

It looks like this is your first PR to kubernetes/kube-state-metrics 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes/kube-state-metrics has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[RiRa12621]

/assign @dgrisonnet

[mrueg]

The solution looks good to me.
Any thoughts on using slices.Sort + slices.Compact similar to #2502 ? This might be simpler than building a separate function for it.

[CatherineF-dev]

The solution looks good to me. Any thoughts on using slices.Sort + slices.Compact similar to #2502 ? This might be simpler than building a separate function for it.

+1

[RiRa12621]

Sure, I'll get that changed tomorrow

[rgarcia89]

@RiRa12621 are you still working on that PR?

[RiRa12621]

Planning to, was just overly busy at day job