landing b_recovery on b_devel

landing b_recovery on b_devel

* bug fixes
 - imports and exports cleanup too early, need refcounts (349, 879, 1045)
 - per-import/export recovery handling (958, 931, 959)
 - multiple last-rcvd slots, for serving multiple FSes (949)
 - connections are again shared between multiple imp/exports (963, 964)
 - "umount -f" would hang if any requests needed to be sent (393, 978)
 - avoid pinning large req buffer by copying for queued messages (989)
 - add "uuid" to "lctl device" command to help upcalls (991)
 - "open" RPCs with transnos would confuse recovery counters (1037)
* major user-visible changes
 - fail out/fail over policy now controlled by the upcall (993)
* protocol changes
 - add OBD_PING to check server availability and failure (954)