Description of problem:
fail [github.com/openshift/origin/test/extended/prometheus/prometheus.go:79]: Unexpected error:
    <errors.aggregate | len:1, cap:1>: [
        {
            s: "promQL query returned unexpected results:\n\nsort_desc((\ncount_over_time(ALERTS{alertname!~\"Watchdog|AlertmanagerReceiversNotConfigured\",alertstate=\"firing\",severity!=\"info\"}[11m8s:1s]) unless\ncount_over_time(ALERTS{alertname=\"AggregatedAPIDown\",name=\"v1alpha1.wardle.example.com\",alertstate=\"firing\"}[11m8s:1s])\n) > 0)\n[\n  {\n    \"metric\": {\n      \"alertname\": \"PodDisruptionBudgetAtLimit\",\n      \"alertstate\": \"firing\",\n      \"namespace\": \"openshift-image-registry\",\n      \"poddisruptionbudget\": \"image-registry\",\n      \"prometheus\": \"openshift-monitoring/k8s\",\n      \"severity\": \"warning\"\n    },\n    \"value\": [\n      1617074354.765,\n      \"328\"\n    ]\n  }\n]",
        },
    ]
    promQL query returned unexpected results:
    
    sort_desc((
    count_over_time(ALERTS{alertname!~"Watchdog|AlertmanagerReceiversNotConfigured",alertstate="firing",severity!="info"}[11m8s:1s]) unless
    count_over_time(ALERTS{alertname="AggregatedAPIDown",name="v1alpha1.wardle.example.com",alertstate="firing"}[11m8s:1s])
    ) > 0)
    [
      {
        "metric": {
          "alertname": "PodDisruptionBudgetAtLimit",
          "alertstate": "firing",
          "namespace": "openshift-image-registry",
          "poddisruptionbudget": "image-registry",
          "prometheus": "openshift-monitoring/k8s",
          "severity": "warning"
        },
        "value": [
          1617074354.765,
          "328"
        ]
      }
    ]
occurred

Version-Release number of selected component (if applicable):
4.8

How reproducible:

Failing since 2021-03-26:
https://prow.ci.openshift.org/job-history/gs/origin-ci-test/logs/release-openshift-ocp-installer-e2e-remote-libvirt-image-ecosystem-s390x-4.8