LU-2832 ptlrpc: cleanup bulk for resend case

LU-2832 ptlrpc: cleanup bulk for resend case

when the request with bulk(ptlrpc_bulk_desc) is resent or replayed,
the stats of the bulk should be cleaned up for it will be reused.

Change-Id: Ie340c8aa43e1a19595c50bed05134537d8d07d74
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-on: http://review.whamcloud.com/5532
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>