[bug ?] PrometheusPushGatewayReporter register more then one JM

[miki haiat]

We have  standalone cluster  with  PrometheusPushGatewayReporter  conflagration.

its seems like we cant register more then one JM to  Prometheus  because of naming uniqueness.

 WARN  org.apache.flink.metrics.prometheus.PrometheusPushGatewayReporter  - There was a problem registering metric numRunningJobs.

java.lang.IllegalArgumentException: Collector already registered that provides name: flink_jobmanager_numRunningJobs