Set diskfs stores as readonly on shutdown before enabling RPCs again.

diff --git a/libdiskfs/init-startup.c b/libdiskfs/init-startup.c
index bf1acf2..700a26e 100644
--- a/libdiskfs/init-startup.c
+++ b/libdiskfs/init-startup.c
@@ -148,6 +148,9 @@ diskfs_S_startup_dosync (mach_port_t handle)
 	  diskfs_set_hypermetadata (1, 1);
 	  _diskfs_diskdirty = 0;
 
+	  diskfs_readonly = 1;
+	  diskfs_readonly_changed (1);
+
 	  ports_resume_class_rpcs (diskfs_protid_class);
 	}