podman detection prints unnecessary outputs to stderr.

[judovana]

When podman existence is detected (#5460), it is using which command, which confirms existence of command on path by printing the full path to stdout. If it is not found, the path is print to stderr.

root@jvanek:/home/jvanek# which docker
/usr/bin/docker
root@jvanek:/home/jvanek# which nonsense
/usr/bin/which: no nonsense in (/root/.local/bin:/root/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/var/lib/snapd/snap/bin)

Where the stdout is handled correctly, the stderr was missed

[judovana]

#5765