Change Dockerfile BASE_REGISTRY

I know it isn't a big deal, but it is also a quick fix. The BASE_REGISTRY in the Dockerfile is set to ARG BASE_REGISTRY=registry1.dsop.io. I expect this should be changed to ARG BASE_REGISTRY=registry1.dso.mil.

If I had the ability to fork to a private repo or something I'd be glad to submit an MR. Is there another way to do that? For stuff like this a git patch seems overkill. It'd take longer to implement than just creating an MR from this issue, some quick WebIDE work and Bob's your uncle.