Fix debug log line for job metrics

[khewonc]

What does this PR do?

Fix an issue where job metrics are missing when the agent uses DEBUG level logging

Motivation

Parsing the job label for job metrics when the agent is set to DEBUG logging results in the following type error:

2020-05-20 19:09:44 UTC | CORE | WARN | (pkg/collector/python/datadog_agent.go:118 in LogMessage) | kubernetes_state:5594cf03e448ecbf | (mixins.py:638) | Error handling metric: kube_job_status_failed - error: not all arguments converted during string formatting

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached

[xornivore]

👍

[stale]

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