Not sure if it's a typo by yourself but the command line switch for a silent install is /q NOT /s
RUNONDEMANDSCAN="" should disable the scan it needs to be set to true to run it RUNONDEMANDSCAN="TRUE"
https://kc.mcafee.com/resources/sites/MCAFEE/content/live/PRODUCT_DOCUMENTATION/ 22000/PD22944/en_US/vse_880_installation_guide_en-us.pdf pages 16 to 19 for more information.
You high network bandwidth utilization is probably not a result of the On Demand Scan but the AUTOUPDATE that runs before the On Demand scan. A default install of VSE has no DATs so after the installation it will download the 100Mb avvdat-XXXX.zip from the ePO server.
I'm not sure how your deploying the packages but one option to gain a bit better control over the process would be to disable the Auto Update and the On Demand tasks and after apply a superDAT to VSE post installation.