Improvement of Issue: "When JobScheduler is not running an error message should only be shown once."

Current Situation

JOC Cockpit remarks with JOC-251 if the JobScheduler is unreachable and ...

• shows the State:unreachable in the status bar on the top
• doesn't alert JobSchedulerConnectionRefusedException (code JOC-402)

This works properly if we have a "standalone" JobScheduler.

For a Passive Cluster...

• JOC Cockpit observes only the state of the primary JobScheduler
• If the backup JobScheduler is active then JOC Cockpit
  • suppresses alerts caused by JobSchedulerConnectionRefusedException (code JOC-402).
  • shows the State:unreachable in the status bar on the top

Desired Behavior

• If the ./events web service response contains a SchedulerStateChanged event then JOC Cockpit should call the ./jobscheduler web service (only with the "jobschedulerId" in the body) to know the state of the current JobScheduler.
• If the ./events web service response contains a CurrentJobSchedulerChanged event then JOC Cockpit should call the ./jobscheduler web service (only with the "jobschedulerId" in the body) to know the state of the current JobScheduler.
• If the state is unreachable then suppress alerts of JobSchedulerConnectionRefusedException (code JOC-402).
• The state in the top status bar should display always (see also JOC-273).