Lower metadata transformer log level

[AlexandreYang]

What does this PR do?

Lower metadata transformer log level.

Motivation

Error log level too severe for this type of issue.

Additional Notes

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

[codecov]

Codecov Report

Merging #5282 into master will increase coverage by 2.84%.
The diff coverage is n/a.

Impacted Files	Coverage Δ
disk/tests/common.py	63.63% <0%> (-36.37%)	⬇️
disk/tests/conftest.py	78.26% <0%> (-17.4%)	⬇️
disk/tests/test_filter.py	96.42% <0%> (-3.58%)	⬇️
apache/datadog_checks/apache/apache.py	89.04% <0%> (-2.9%)	⬇️
disk/datadog_checks/disk/disk.py	84.4% <0%> (-2.3%)	⬇️
apache/tests/conftest.py	100% <0%> (ø)	⬆️
...ts/tooling/configuration/consumers/test_example.py
...checks_dev/tests/plugin/test_environment_runner.py
riakcs/datadog_checks/riakcs/riakcs.py
oracle/tests/test_oracle.py
... and 615 more