jjb: lava: keep track of job exit status and configuration

jjb: lava: keep track of job exit status and configuration

Completely rework the system trigger jobs.

Before those changes a failed sub-job would make the umbrella job fail
once but the next time the umbrella job runs, it would see no new
commit, omit the schedule the sub-job again, and return success.
Failures were forgotten after one day.

We now save on the workspace the exit status and configuration of every
sub-job. This way we can avoid re-running sub-jobs that have jailed in
the past and haven't changed since. An umbrella jobs containing such
sub-job will now directly marked as failed.

The umbrella job will keep the failed status until all sub-jobs succeed.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>