Duplicate fields with ScalaObjectMapper

When there is a `case class` with `BeanProperty`-annotated field, the following code sometimes generates JSON with duplicate fields. For example, `pId` field gets serialized twice, as `pId` and `pid`.

```
private val mapper = {
val objectMapper = new ObjectMapper with ScalaObjectMapper
objectMapper.registerModule(DefaultScalaModule)
objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL)
objectMapper
}

def toJson[A <: AnyRef](a: A): String = {
mapper.writeValueAsString(a)
}
```

It's impossible to remove `BeanProperty` annotation, because it's needed by another library. Also it's impossible to set `BeanProperty` on every field and remove `ScalaObjectMapper`, as such changes are numerous and would likely result in other compatibility issues. What's the proper way to fix this problem?