Admin service returns OK and "Added" for updated stage configs without updating them

[laserval]

POSTing a stage configuration with the admin-service, then changing it and POSTing again will cause a stage restart but no configuration update.

[laserval]

I am having a look at this and have found that StageGroup has some issues with adding/removing stages, due to using a Set of stages that are identified by their hashCode, which happens to depend on their modification date. If for some reason a stage config is added twice to a group without the group being written to the database, the order the configurations are applied is not guaranteed.