Pidns: make full use of xxx_vnr() calls

Some time ago the xxx_vnr() calls (e.g.  pid_vnr or find_task_by_vpid) were
_all_ converted to operate on the current pid namespace.  After this each call
like xxx_nr_ns(foo, current->nsproxy->pid_ns) is nothing but a xxx_vnr(foo)
one.

Switch all the xxx_nr_ns() callers to use the xxx_vnr() calls where
appropriate.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Reviewed-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/sys.c b/kernel/sys.c
index 5a61f80..a626116 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -991,17 +991,14 @@
 	else {
 		int retval;
 		struct task_struct *p;
-		struct pid_namespace *ns;
-
-		ns = current->nsproxy->pid_ns;
 
 		read_lock(&tasklist_lock);
-		p = find_task_by_pid_ns(pid, ns);
+		p = find_task_by_vpid(pid);
 		retval = -ESRCH;
 		if (p) {
 			retval = security_task_getpgid(p);
 			if (!retval)
-				retval = task_pgrp_nr_ns(p, ns);
+				retval = task_pgrp_vnr(p);
 		}
 		read_unlock(&tasklist_lock);
 		return retval;