pid namespaces: rename child_reaper() function

Rename the child_reaper() function to task_child_reaper() to be similar to
other task_* functions and to distinguish the function from 'struct
pid_namspace.child_reaper'.

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Herbert Poetzel <herbert@13thfloor.at>
Cc: Kirill Korotaev <dev@sw.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/exec.c b/fs/exec.c
index 6ffb769..4b5bbb8 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -775,7 +775,7 @@
 	 * Reparenting needs write_lock on tasklist_lock,
 	 * so it is safe to do it under read_lock.
 	 */
-	if (unlikely(tsk->group_leader == child_reaper(tsk)))
+	if (unlikely(tsk->group_leader == task_child_reaper(tsk)))
 		task_active_pid_ns(tsk)->child_reaper = tsk;
 
 	zap_other_threads(tsk);