Don't allow snapshot-of-snapshot

Don't allow snapshot-of-snapshot because it would confuse the logic.
Snapshots of snapshots will be allowed in further patch, with special
support for them.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 lib/metadata/lv_manip.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: LVM2.2.02.85/lib/metadata/lv_manip.c
===================================================================
--- LVM2.2.02.85.orig/lib/metadata/lv_manip.c	2011-06-24 18:58:26.000000000 +0200
+++ LVM2.2.02.85/lib/metadata/lv_manip.c	2011-06-24 18:58:31.000000000 +0200
@@ -3564,7 +3564,7 @@ again:
 					  "Use --virtualsize.");
 				return 0;
 			}
-			if (lv_is_cow(org)) {
+			if (lv_is_cow(org) || lv_is_multisnap_cow(org)) {
 				log_error("Snapshots of snapshots are not "
 					  "supported yet.");
 				return 0;