columnstore script needs to be resilient

Stepping through the process to install CS for the SE training next week, DT & I noticed a problem where running 'columnstore start' seemed to do nothing. It turned out it was the way we were running it, via a remote ssh command like 'ssh me@machine columnstore start'. Our shells went away right after executing the script, which killed the background processes the columnstore script started.

This is normally not a problem but it's also non-standard behavior for a service script. Fixing it should be easy; just have columnstore disown the run.sh process it starts. (the bash built-in command 'disown')