iotile-gateway throwing away scan packet fields?

Somewhere in `iotile-gateway`, `scan` packets are being modified before it ends up at a consumer (via `hw.scan()`, for example).

We discovered this because some of our systems rely on finding the `signal_strength` field in a packet to collect diagnostics.

I am looking for where in coretools this is happening and will update if I find it (opening a ticket now in case anyone finds it faster!)