Viper: produce a perms error for config file

[djmitche]

This updates Viper to a version containing
DataDog/viper#26 which returns a permissions
error if the config file cannot be read due to a permissions problem.
Previously this implementation unconditionally returned a "not found"
error which produced a deceptive message for the user.

Motivation

Better error messages

Possible Drawbacks / Trade-offs

This gets us deeper into our dependency on our fork of Viper.

Describe how to test/QA your changes

Run an agent in a situation where its configuration is inaccessible due to permissions errors (such as chmod 000 /etc/datadog-agent/datadog.yaml). You should see

Error: unable to set up global agent configuration: cannot access the Datadog config file (open /etc/datadog-agent/datadog.yaml: permission denied); try running the command under the same user as the Datadog Agent

do this on both WIndows and linux/mac.

Reviewer's Checklist

• If known, an appropriate milestone has been selected; otherwise the Triage milestone is set.
• Use the major_change label if your change either has a major impact on the code base, is impacting multiple teams or is changing important well-established internals of the Agent. This label will be use during QA to make sure each team pay extra attention to the changed behavior. For any customer facing change use a releasenote.
• A release note has been added or the changelog/no-changelog label has been applied.
• Changed code has automated tests for its functionality.
• Adequate QA/testing plan information is provided if the qa/skip-qa label is not applied.
• At least one team/.. label has been applied, indicating the team(s) that should QA this change.
• If applicable, docs team has been notified or an issue has been opened on the documentation repo.
• If applicable, the need-change/operator and need-change/helm labels have been applied.
• If applicable, the k8s/<min-version> label, indicating the lowest Kubernetes version compatible with this feature.
• If applicable, the config template has been updated.

[sgnn7]

Note: Some build failures seem legitimate on the PR

[djmitche]

Looks like this is causing issues reading .hcl files in NPM.

[djmitche]

• integration tests are failing due to an etcd issue that was fixed on main yesterday
• linux kitchen tests are intermittents
• windows kitchen tests are Remove legacy container metrics collection code #12971.

[djmitche]

..and ci/circleci: build_iot_agent and ci/circleci: build_images aren't running because the integration tests aren't. So I'm overriding branch protection.