Changes

testenv: run daemons with 'ulimit -c unlimited'

Prepare to support getting core files without having systemd-coredump
installed, as we plan to uninstall it from the jenkins servers to make
retrieving coredumps for other jobs feasible again.

When starting daemons, set the maximum core file size to unlimited.
Otherwise it might be at 0, resulting in no core files getting
generated.

I have considered using resource.setrlimit() on the python process
instead, but this wouldn't work when spawning the daemons inside the
podman container.

Change-Id: Ideaf0386c8d6111c2634f276f926e976023ff511