Scan of int value into `interface{}` fails

Please answer these questions before submitting your issue. Thanks!

### What version of Cassandra are you using?
3.0.7

### What version of Gocql are you using?
latest

### What did you do?
Same setup as in #1330

Modified program to read as:

```go
var id gocql.UUID
data := make(map[string]interface{})
if !it.Scan(&id, &data) {
break
}
```

### What did you expect to see?
A map of string to int values.

### What did you see instead?
The error message
`can not unmarshal int into *interface {}`

Start by reproducing the reported Scan call with a gocql.UUID and map[string]interface{} against Cassandra 3.0.7, then trace the scan and unmarshal path that produces "can not unmarshal int into *interface {}". Done means the query scans successfully and returns a map whose values are integers.

Written by the indexing model from the issue text.