Description of problem:
After deploying logging stack, fluentd and kibana are not able to resolve elasticsearch hostname

Fluentd logs :
2021-03-28T04:25:16.095607233Z 2021-03-28 04:25:16 +0000 [warn]: [default] failed to flush the buffer. retry_time=3 next_retry_seconds=2021-03-28 04:25:20 +0000 chunk="5be8a1fd530465ad135bed371a2c729a" error_class=Fluent::Plugin::ElasticsearchOutput::RecoverableRequestFailure error="could not push logs to Elasticsearch cluster ({:host=>\"elasticsearch.openshift-logging.svc.cluster.local\", :port=>9200, :scheme=>\"https\"}): Couldn't resolve host name"

Kibana logs:
2021-03-28T04:24:50.963666757Z {"type":"log","@timestamp":"2021-03-28T04:24:50Z","tags":["warning","elasticsearch","admin"],"pid":117,"message":"No living connections"}
2021-03-28T04:24:53.469808289Z {"type":"log","@timestamp":"2021-03-28T04:24:53Z","tags":["warning","elasticsearch","admin"],"pid":117,"message":"Unable to revive connection: https://elasticsearch.openshift-logging.svc.cluster.local:9200/"}


Version-Release number of selected component (if applicable):
4.7

How reproducible:
100%

Steps to Reproduce:
1. Use internal domain for RHOCP 4.7
2. Install Red Hat OpenShift Logging
3. Check fluentd and kibana pod logs

Actual results:
Fluentd and kibana are not able to resolve elasticsearch's hostname

Expected results:
Fluentd and kibana should be able to resolve elasticsearch hostname

Additional info: