fsnotify: fsnotify_obtain_group should be fsnotify_alloc_group

fsnotify_obtain_group was intended to be able to find an already existing
group.  Nothing uses that functionality.  This just renames it to
fsnotify_alloc_group so it is clear what it is doing.

Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 59065e7..813274d 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -937,7 +937,7 @@
 {
 	int i;
 
-	audit_tree_group = fsnotify_obtain_group(0, &audit_tree_ops);
+	audit_tree_group = fsnotify_alloc_group(0, &audit_tree_ops);
 	if (IS_ERR(audit_tree_group))
 		audit_panic("cannot initialize fsnotify group for rectree watches");