Description of problem:
eanbled User Workload Monitoring and created user-workload-monitoring-config configmap to set prometheus.retention as 48h, but retention time is still 15d for prometheus-user-workload pod.
Note: default retention time for statefulset prometheus-k8s under openshift-monitoring is 15d
# kubectl -n openshift-user-workload-monitoring get cm user-workload-monitoring-config -oyaml
apiVersion: v1
data:
  config.yaml: |
    prometheus:
      retention: 48h
kind: ConfigMap
metadata:
  creationTimestamp: "2020-07-01T08:26:31Z"
  managedFields:
  - apiVersion: v1
    fieldsType: FieldsV1
    fieldsV1:
      f:data:
        .: {}
        f:config.yaml: {}
    manager: oc
    operation: Update
    time: "2020-07-01T08:26:31Z"
  name: user-workload-monitoring-config
  namespace: openshift-user-workload-monitoring

# for i in $(kubectl -n openshift-user-workload-monitoring get sts --no-headers | awk '{print $1}'); do echo $i; kubectl -n openshift-user-workload-monitoring get sts $i -oyaml | grep -i retention -A1; done
prometheus-user-workload
        - --storage.tsdb.retention.time=15d
        - --web.enable-lifecycle
thanos-ruler-user-workload
        - --tsdb.retention=24h
        - --label=thanos_ruler_replica="$(POD_NAME)"

#  for i in $(kubectl -n openshift-user-workload-monitoring get pod | grep prometheus-user-workload | awk '{print $1}'); do echo $i; kubectl -n openshift-user-workload-monitoring get pod  $i -oyaml | grep -i retention -A1; done
prometheus-user-workload-0
    - --storage.tsdb.retention.time=15d
    - --web.enable-lifecycle
prometheus-user-workload-1
    - --storage.tsdb.retention.time=15d
    - --web.enable-lifecycle

# kubectl -n openshift-monitoring get sts prometheus-k8s  -oyaml | grep -i retention -A1
        - --storage.tsdb.retention.time=15d
        - --web.enable-lifecycle



Version-Release number of selected component (if applicable):
4.6.0-0.nightly-2020-06-30-000342

How reproducible:
always

Steps to Reproduce:
1. see the description
2.
3.

Actual results:


Expected results:


Additional info: