Remote library must be restarted between test executions if tests are running on same machine

[psaikkonen]

If the remote library server and tests are running on the same machine, the server must be restarted between test executions. If the server is not restarted, test applications will launch behind other windows, causing tests to fail when robot is trying to interact with them.

It seems that PrimaryStageApplications stage attaches itself to the remote library process, and doesn't close properly. The same hidden stage is then reused when applications are launched for the next execution, so they will start behind the terminal window.