coredump: turn off coredump collection only when PID 1 crashes, not w…

[poettering]

…hen journald crashes

As suggested:

https://github.com/systemd/systemd/pull/3783/files/5157879b757bffce3da0a68ca207753569e8627d#r71906971

[poettering]

cc @evverx

[evverx]

Many thanks!
Works fine:

-bash-4.3# kill -ABRT $(systemctl show --property MainPID --value systemd-journald); sh -c 'kill -ABRT $$'; kill -ABRT 1; sh -c 'kill -ABRT $$'

strace: Process 1 attached
pause(strace: Process 1 detached
 <detached ...>

-bash-4.3# ls /var/lib/systemd/coredump/
core.sh.0.3de40e6f57144d7b88d57703f2767157.252.1469345710000000000000.xz
core.systemd-journal.0.3de40e6f57144d7b88d57703f2767157.132.1469345710000000.xz
core.systemd.0.3de40e6f57144d7b88d57703f2767157.257.1469345711000000.xz

bash-4.3# dmesg
...
[   87.507118] systemd-coredump[259]: Due to PID 1 having crashed coredump collection will now be turned off.
[   90.603437] systemd-coredump[254]: Failed to log coredump: Connection refused
[   99.963005] systemd-coredump[259]: Detected coredump of the journal daemon or PID 1, diverted to /var/lib/systemd/coredump/core.systemd.0.3de40e6f57144d7b88d57703f2767157.257.1469345711000000.xz.
[  100.200219] systemd-coredump[251]: Detected coredump of the journal daemon or PID 1, diverted to /var/lib/systemd/coredump/core.systemd-journal.0.3de40e6f57144d7b88d57703f2767157.132.1469345710000000.xz.