configure karaf.name/runtime.id from docker env, and fix users.properties

In the docker fabric8 instance root container, I was unable to add the insight-console profile due to:
can't create ES node: "Could not resolve placeholder 'runtime.id'"

this was caused by the Dockerfile deleting the karaf.name and runtime.id from etc/system.properties

I changed the Dockerfile and startup.sh to replace the setting based on the environment variable instead of deleting the settings from the Dockerfile.
Also changed the user.properties modification, which seemed erroneous.