staging/lustre/ptlrpc: update imp_known_replied_xid on resend-replay

The imp_known_replied_xid should be updated when try to resend
an already replied replay request, because the xid of this replay
request could be less than current imp_known_replied_xid.

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-on: http://review.whamcloud.com/22776
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8645


Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>