cgroup: do not set cgroup parent when rootless and cgroupfs

do not set the cgroup parent when running as rootless with cgroupfs,
even if cgroup v2 is used.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1947999

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

libpod/container_internal_linux.go

@@ -2216,7 +2216,7 @@ func (c *Container) getOCICgroupPath() (string, error) {
 	}
 	cgroupManager := c.CgroupManager()
 	switch {
-	case (rootless.IsRootless() && !unified) || c.config.NoCgroups:
+	case (rootless.IsRootless() && (cgroupManager == config.CgroupfsCgroupsManager || !unified)) || c.config.NoCgroups:
 		return "", nil
 	case c.config.CgroupsMode == cgroupSplit:
 		if c.config.CgroupParent != "" {

test/system/420-cgroups.bats

@@ -24,6 +24,11 @@ load helpers
     run_podman container inspect --format '{{.HostConfig.CgroupManager}}' myc
     is "$output" "$other" "podman preserved .HostConfig.CgroupManager"
 
+    if is_rootless && test $other = cgroupfs ; then
+        run_podman container inspect --format '{{.HostConfig.CgroupParent}}' myc
+        is "$output" "" "podman didn't set .HostConfig.CgroupParent for cgroupfs and rootless"
+    fi
+
     # Restart the container, without --cgroup-manager option (ie use default)
     # Prior to #7970, this would fail with an OCI runtime error
     run_podman start myc