[#158] pkg/client: Ignore EOF on buffer copy in object.Put

There is a issue when user sends payload chunk to the neofs
node, but node closes connection earlier, e.g. node can return
error as soon as it checked ACL permission and denied request.

In this case client will receive EOF error and it produces
`could not send payload bytes to Put object stream` error, but
in fact there is different error.

If we ignore EOF there then `stream.CloseAndRecv()` return
correct error message later.

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/client/object.go

@@ -232,7 +232,8 @@ func (c *Client) putObjectV2(ctx context.Context, p *PutObjectParams, opts ...Ca
 	}
 
 	// copy payload from reader to stream writer
-	if _, err := io.CopyBuffer(w, rPayload, make([]byte, chunkSize)); err != nil {
+	_, err = io.CopyBuffer(w, rPayload, make([]byte, chunkSize))
+	if err != nil && !errors.Is(errors.Cause(err), io.EOF) {
 		return nil, errors.Wrap(err, "could not send payload bytes to Put object stream")
 	}