Currently while a job is running we set `pid = SchedulerPid`,
`succeed = false` and `execution_finish=NOW()` and it leads to
confusion when querying either `timescaledb_information.job_errors`
or `timescaledb_information.job_history` views showing in the
`err_message = job crash detected, see server logs`. This information
is wrong and create confusion.
Fixed it by setting `succeed=NULL` and `pid=NULL` when the scheduler
launch the job and then when the job worker start to work then set
`pid=MyProcPid` (the worker PID) meaning that the job started and
didn't finished yet, and at the end of the execution we set
`succeed=TRUE or FALSE` and the `execution_finish=NOW()` to mark the
end of the job execution. Also adjusted the views to expose the
information properly.
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