NFSv4.1: Reinitialise sequence results before retransmitting a request

If we have to retransmit a request, we should ensure that we reinitialise
the sequence results structure, since in the event of a signal
we need to treat the request as if it had not been sent.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: stable@vger.kernel.org