Description of problem:

The alert `FluentdNodeDown` is always firing. The rule is:

    - alert: FluentdNodeDown
      annotations:
        message: Prometheus could not scrape fluentd {{ $labels.instance }} for more
          than 10m.
        summary: Fluentd cannot be scraped
      expr: |
        absent(up{job="fluentd"} == 1)
      for: 10m
      labels:
        service: fluentd
        severity: critical

In 5.3, the collector name is changed from `fluentd` to `collector`, maybe the expr should be `absent(up{job="collector"} == 1)`

Version-Release number of selected component (if applicable):

cluster-logging.5.3.0-46 

How reproducible:

Always

Steps to Reproduce:
1. deploy logging 5.3
2. check alerts in openshift console
3.

Actual results:

Expected results:

Additional info: