Set WORKER_MAX_PAYLOAD_MB on RTM

[stuartc]

User story

The worker now supports limiting the max payload size when completing steps. The default is 10MB, but locally the MAX_DATACLIP_SIZE_MB may be set.

So when running the RTM locally (i.e. in dev mode), we should set WORKER_MAX_PAYLOAD_MB to the same as MAX_DATACLIP_SIZE_MB