podman 2.x halved the pid limits by default from 4096 to 2048

[Michele Baldessari]

With both podman 2.0.x and podman 2.2.x I observe the following behaviour:
[root@ctrl-1-0 containers]# podman run --rm -it --net=host --name 'pids' edecd409281d sh -c 'cat /sys/fs/cgroup/pids/pids.max'
2048
[root@ctrl-1-0 containers]# rpm -q podman
podman-2.2.1-3.module+el8.3.1+9392+c5f6d096.x86_64

With podman-1.6.4 the global default pid-limits was hardcoded to 4096 and we had no way to tweak it.

With podman 2.X it is possible to override this in /etc/containers/containers.conf like this:
[root@ctrl-1-0 containers]# more /etc/containers/containers.conf
[containers]
pids_limit=6666

[root@ctrl-1-0 containers]# podman run --rm -it --net=host --name 'pids' edecd409281d sh -c 'cat /sys/fs/cgroup/pids/pids.max'
6666

We should make sure that at the very least we default to 4096 and let the operator override it.

[Michele Baldessari (michele)]

https://review.opendev.org/c/openstack/tripleo-heat-templates/+/774513
https://review.opendev.org/c/openstack/tripleo-ansible/+/774512