Land b_recovery (other than WIP lock-replay work).

Land b_recovery (other than WIP lock-replay work).

- b=512,others: fully reactivate OST imports after reconnection.
- b=513(partial): make sure client sees out -ENOTCONN from mds_handle
- b=515: more graceful error handling for truncating on dead OST
- b=474: don't error out just because a file is striped across a dead OST; only
         if we actually try to access it
- b=410: fix garbage sizes when stat(2)ing a file that includes a stripe on a
         dead OST
- print console diagnostic for completion-timeout client recovery
- MSG_RESENT for requests that were retransmitted