LU-13165 mdt: MSG_RESENT can be improperly cleared.

LU-13165 mdt: MSG_RESENT can be improperly cleared.

req_can_reconstruct() can return -EPROTO, it means that
original request was processed and reply was received.

Change-Id: I06ba9aa24821f414777d38e9ca606652b172e92c
Fixes: 23773b32bf ("LU-11444 ptlrpc: resend may corrupt the data")
Cray-bug-id: LUS-7972
Signed-off-by: Andriy Skulysh <c17819@cray.com>
Reviewed-by: Vitaly Fertman <c17818@cray.com>
Reviewed-by: Alexander Boyko <c17825@cray.com>
Reviewed-on: https://review.whamcloud.com/37296
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexandr Boyko <c17825@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>