podman-remote: do not check for cgroupv2

With the remote client on linux we should not check for cgroups and hard
fail if it is not v2. Only the server side matters not the client.

The problem can be reproduced with:
unshare -rm sh -c "mount -t tmpfs none /sys/fs/cgroup  && ./bin/podman --remote ps"

I did not add a regression test as it does not seem to fit well into a
test suite, over mounting cgroups seems like not a good idea.

Fixes: #29241

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

cmd/podman/root_cgroups_linux.go

@@ -1,13 +1,18 @@
-//go:build linux
+//go:build linux && !remote
 
 package main
 
 import (
 	"github.com/sirupsen/logrus"
 	"go.podman.io/common/pkg/cgroups"
+	"go.podman.io/podman/v6/cmd/podman/registry"
 )
 
 func checkSupportedCgroups() {
+	if registry.IsRemote() {
+		// In remote mode we should not error for missing cgroups as just the server needs it.
+		return
+	}
 	unified, err := cgroups.IsCgroup2UnifiedMode()
 	if err != nil {
 		logrus.Fatalf("Error determining cgroups mode")

cmd/podman/root_cgroups_unsupported.go

@@ -1,7 +1,7 @@
-//go:build !linux
+//go:build !linux || remote
 
 package main
 
 func checkSupportedCgroups() {
-	// NOP on Non Linux
+	// NOP on Non Linux or Remote
 }