When fetch pid counts the contianer can be in an invalid state sometimes

Signed-off-by: James Sturtevant <jstur@microsoft.com>
(cherry picked from commit 2095093)
Signed-off-by: Kirtana Ashok <kiashok@microsoft.com>

cmd/containerd-shim-runhcs-v1/task_hcs.go

@@ -545,6 +545,9 @@ func (ht *hcsTask) Pids(ctx context.Context) ([]runhcsopts.ProcessDetails, error
 	// Get the guest pids
 	props, err := ht.c.Properties(ctx, schema1.PropertyTypeProcessList)
 	if err != nil {
+		if isStatsNotFound(err) {
+			return nil, errors.Wrapf(errdefs.ErrNotFound, "failed to fetch pids: %s", err)
+		}
 		return nil, err
 	}