nfsd: make laundromat network namespace aware

This patch moves laundromat_work to nfsd per-net context, thus allowing to run
multiple laundries.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index a356ea3..227b93e 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -79,6 +79,8 @@
 	 */
 	struct list_head client_lru;
 	struct list_head close_lru;
+
+	struct delayed_work laundromat_work;
 };
 
 extern int nfsd_net_id;