SUNRPC: Ensure that we honour autoclose before attempting to reconnect

If the XPRT_CLOSE_WAIT flag is set, we need to ensure that we call
xprt->ops->close() while holding xprt_lock_write() before we can
start reconnecting.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>