URDF w/o SLAM pack does not load properly

[rencheckyoself]

I am working on some simulation stuff and wanted to use the provided rr_openrover_description files without the SLAM Pack so I could add our payload layout instead. I was starting by using the description-4wd.launch to view the URDF, however passing the argument config:=4WD_Rover results in an error:
ros.rosconsole_bridge.console_bridge: Failed to find root link: Two root links found: [base_footprint] and [slam_pack_mount_point]

After looking into it some, I was able to get it to launch properly by modifying the rr_openrover_description/urdf/accessories/accessories.urdf.xacro file. I moved the xacro:include line inside of the if statement so the file is only included if the With_SLAM config argument is passed.