Manage mount lifecycle and remove cached state

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/server/sandbox_run.go

@@ -41,6 +41,7 @@ import (
 	customopts "github.com/containerd/cri/pkg/containerd/opts"
 	ctrdutil "github.com/containerd/cri/pkg/containerd/util"
 	"github.com/containerd/cri/pkg/log"
+	"github.com/containerd/cri/pkg/netns"
 	sandboxstore "github.com/containerd/cri/pkg/store/sandbox"
 	"github.com/containerd/cri/pkg/util"
 )
@@ -104,7 +105,7 @@ func (c *criService) RunPodSandbox(ctx context.Context, r *runtime.RunPodSandbox
 		// handle. NetNSPath in sandbox metadata and NetNS is non empty only for non host network
 		// namespaces. If the pod is in host network namespace then both are empty and should not
 		// be used.
-		sandbox.NetNS, err = sandboxstore.NewNetNS()
+		sandbox.NetNS, err = netns.NewNetNS()
 		if err != nil {
 			return nil, errors.Wrapf(err, "failed to create network namespace for sandbox %q", id)
 		}