Reorder error cases in MultiFileStorage::open to catch no more free frames before too many write buffers.
Reorder error cases in MultiFileStorage::open to catch no more free frames before too many write buffers.

SMatsushi/RAMCloud,jblomer/ramcloud,jblomer/ramcloud,utah-scs/RAMCloud,utah-scs/RAMCloud,jblomer/ramcloud,anirajk/RAMCloud,SMatsushi/RAMCloud,jblomer/ramcloud,utah-scs/RAMCloud,anirajk/RAMCloud,utah-scs/RAMCloud,jblomer/ramcloud,utah-scs/RAMCloud,utah-scs/RAMCloud,SMatsushi/RAMCloud,anirajk/RAMCloud,SMatsushi/RAMCloud,SMatsushi/RAMCloud,jblomer/ramcloud,SMatsushi/RAMCloud,anirajk/RAMCloud,anirajk/RAMCloud,anirajk/RAMCloud