[z2092] Prevent saving/loading/init capture points in instances

Reason for this are:
1) We don't want them saved/loaded between bg games
2) Saving cp slider is done by go id and would not work for instances
3) There are visual-only capture points in bg (eots)
4) It would be possible to only enable the capture points on bg start

TODO: Move this to OutdoorPvP base class

(based on commit [12135] - 536175e)

(based on commit [s1792] - db83495)