fix(builder): decouple deis-builder now that router is fronting it

Now that we have a router in front of deis-builder, there is no need to have it coupled to the controller.  To test:

1. `make -C controller restart` and note how the builder comes down
2. Destroy and recreate builder with the new unit file
3. `make -C controller restart` and note how builder is unaffected

Refs #985.