NFSv4.1: Don't decrease the value of seq_nr_highest_sent

NFSv4.1: Don't decrease the value of seq_nr_highest_sent

commit 8875401c50febe47635373e224aca6f199feef0c upstream.

When we're trying to figure out what the server may or may not have seen
in terms of request numbers, do not assume that requests with a larger
number were missed, just because we saw a reply to a request with a
smaller number.

Fixes: 9f02f6180987 ("NFSv4.1: Avoid false retries when RPC calls are interrupted")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>