Duplicate statsd metrics are sent when loading lzo files

[istreeter]

The KinesisS3Emitter has a callback function which does the statsd reporting after successfully uploading files to S3.

However, the callback is called inside a foreach loop. For lzo compression, this means it is called after the .lzo file is uploaded and also after the .lzo.index file is uploaded. Whereas we should only call it once.

I'll be honest, I've not actually tested this. This is just based on looking at the code.