I'm not sure VDI is supported, but I've asked on my end. Might work anyway.
Still, there are two kinds of sign in. One for product activation and one for services.
For the former, you need to activate according to one of the documented methods. Also, you need to be aware of deployment issues when using an image. See Common Deployment Options and Methods — Enterprise Administration Guide.
If the sign in screen is for services, disable all services as described here: Service and Online Feature Configuration — Enterprise Administration Guide
hth,
Ben