NFSv4: Clean up the support for returning multiple delegations

Add a flag to mark delegations as requiring return, then run a garbage
collector. In the future, this will allow for more flexible delegation
management, where delegations may be marked for return if it turns out
that they are not being referenced.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index d8e062f..bd4c3dd 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2433,7 +2433,7 @@
 {
 	struct nfs_server *server = NFS_SB(sb);
 
-	nfs_return_all_delegations(sb);
+	nfs_super_return_all_delegations(sb);
 	kill_anon_super(sb);
 
 	nfs4_renewd_prepare_shutdown(server);