[Bug 1087700] lost signals when sending lots of signals using --sig-proxy to docker

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1087700

--- Comment #5 from Lukas Doktor  ---
This one was about using `docker kill` very quickly/in parallel, which results
in missing signals in container, even when you use only the "safe" signals. So
documentation won't fix this issue (well you can add 1s wait in `docker kill`
;-) but I believe there is a better solution.