tests: disable coredumps in `conds-trigger`

tests: disable coredumps in `conds-trigger`

After adding some more tests in `conds-trigger`, some CI jobs would
start to fail randomly while running that test, with the Jenkins runner
process seemingly crashing.  Digging a little bit revealed that many
processes (including `systemd-coredump`) would get OOM-killed.

What I think happens is that the many quickly crashing `conds-triggers`
processes cause many `systemd-coredump` processes to get started, which
causes too much memory to be consumed.

It's just wasteful to generate core dumps while running this test
anyway, so disable them.  Use `setrlimit()` in the code path that we
know is going to lead to a crash.

I considered calling `ulimit -c 0` in the bash script that calls all
this, but I would prefer to disable core dumps in the narrowest scope
possible, so that we don't disable them for the code that's not supposed
to crash.

Change-Id: I69bf206cf0afed26f6db65e7fb7e70e9dbe7c053
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/13325
Reviewed-by: Kienan Stewart <kstewart@efficios.com>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins <jenkins@lttng.org>