Add index tagging to cfwConnectionStatValue

[ChristineTChen]

What does this PR do?

Fixes tag for cfwConnectionStatValue and cfwHardwareStatusValue

Motivation

The tags by OID/column were not resolving properly. Using index works better.

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 #6897 into master will increase coverage by 7.02%.
The diff coverage is 100.00%.

Impacted Files	Coverage Δ
snmp/tests/test_profiles.py	99.78% <100.00%> (ø)
datadog_checks_dev/tests/test_utils.py
dns_check/tests/test_dns_check.py
directory/tests/conftest.py
envoy/datadog_checks/envoy/metrics.py
rethinkdb/tests/unit/test_version.py
cisco_aci/datadog_checks/cisco_aci/__about__.py
...os_slave/datadog_checks/mesos_slave/mesos_slave.py
...er/datadog_checks/openstack_controller/__init__.py
gunicorn/datadog_checks/gunicorn/gunicorn.py
... and 808 more