Checkmk Werk 7477: job: Gracefully handle long running cronjobs

ID: 7477 Title: job: Gracefully handle long running cronjobs Component: Checks & agents Level: 1 Class: Bug fix Version: 1.6.0i1 Previously mk_job got confused when a job was started while a job with the same Identity was still running. The mk_job script can now handle these cases. The corresponding check plugin will apply the age levels to the longest runnging job, and additionally display the stats of the last completed job.