procfs: Print task uids and gids in the userns that opened the proc file

Instead of using current_userns() use the userns of the opener
of the file so that if the file is passed between processes
the contents of the file do not change.
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

fs/proc/array.c

@@ -162,7 +162,7 @@ static inline const char *get_task_state(struct task_struct *tsk)
 static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
 				struct pid *pid, struct task_struct *p)
 {
-	struct user_namespace *user_ns = current_user_ns();
+	struct user_namespace *user_ns = seq_user_ns(m);
 	struct group_info *group_info;
 	int g;
 	struct fdtable *fdt = NULL;