Reference implementation of RPC client interface doesn't have correct queryRecord struct

Noticed this while working on a C++ implementation of the serf RPC interface. Per the documentation, the queryRecord has the following content:

```
{"Seq": 50, "Error": ""}
{
"Event": "query",
"ID": 1023,
"LTime": 125,
"Name": "load",
"Payload": "15m",
}
```

The go implementation of queryRecord (https://github.com/hashicorp/serf/blob/master/client/const.go#L157) appears to be incorrect:

```
type queryRecord struct {
Type string
From string
Payload []byte
}
```

In my C++ implementation I've verified that the struct sent by the serf agent has these fields.