mds: note MDiscoverReply encoding change in corpus

Signed-off-by: Sage Weil <sage@inktank.com>

diff --git a/ceph-object-corpus b/ceph-object-corpus
index d9870cdfd89d0d1b791bfc23dce3f263d3214370..e30f68577d9fc788f8b260bc56ba2cb9b2c954a7 160000 (submodule)
--- a/ceph-object-corpus
+++ b/ceph-object-corpus
@@ -1 +1 @@
-Subproject commit d9870cdfd89d0d1b791bfc23dce3f263d3214370
+Subproject commit e30f68577d9fc788f8b260bc56ba2cb9b2c954a7