- Use refcounting to control lifetime of bulk descriptors.

- Use refcounting to control lifetime of bulk descriptors.
- Add some LDLM timeout #warnings for future reference.
- Make all bulk-desc cleanup happen asynchronously, for cleaner interrupt (and
  later timeout) handling.
- Have OSC wait for brw_write reply before beginning bulk operations, for
  symmetry with brw_read and general niceness.
- Fix reply-for-freed-request check to use proper XID width.
- Use l_killable_pending in ptlrpc_check_bulk_sent, for consistency. (Also in the
  new ptlrpc_check_bulk_received sibling.)