added radioactivity field (from linux.com)

## Ready State: Yes

https://imagex.atlassian.net/browse/LDC-236

Related PR:  https://github.com/imagex/imagex_installkit/pull/50

## Requirements & Dependencies

* Requires radioactivity module

## Deployment Instructions

* Merge code.

## Usage/Test Instructions

* Ensure radioactivity field is part of common_fields for imagex install kit