[roofit] fix memory leak in RooCacheManager
[roofit] fix memory leak in RooCacheManager

When other object was already set with such properties,
newly created object was lost

olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root