dump: clean up shared_fdtable

It's cleaned up accoding with following statements:
* files_id can't be zero (look at dump_task_kobj_ids)
* item->ids is allocated for all non-dead tasks
* a parent can't be dead

In addition here is a tiny coding stype fix.

Fixes: 475bb1e7 ("rst: Evaluate per-task clone mask early")
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/pstree.h

@@ -32,11 +32,10 @@ struct pstree_item {
 	struct rst_info		rst[0];
 };
 
-static inline int shared_fdtable(struct pstree_item *item) {
-	return (item->parent && item->parent->state != TASK_HELPER &&
-		item->ids &&
-		item->parent->ids &&
-		item->ids->files_id &&
+/* ids is alocated and initialized for all alive tasks */
+static inline int shared_fdtable(struct pstree_item *item)
+{
+	return (item->parent &&
 		item->ids->files_id == item->parent->ids->files_id);
 }