When a job is started with xml-command <start_job> and the database is switched off the JobScheduler does not try to connect continuously

When a job is started and the database is switched off the scheduler does not try to connect continuously.
As a result when the database is switched on the scheduler does not reconnect to the database.

TODO:
When a job is started with xml-command <start_job> and the database is switched off the xml-command is terminated with an error.
JobScheduler tries to connect to the database only once.
The JobScheduler can't start a job without a database.