Small fixes : workers claim ennemy room + Cannonns keep shooting + sometimes, ennemy kobold can claim claimed walls

To test this patch, the most simple is to play multiplayer map small free for all (it is the same as multiplayer small but no alliance)
With player 2, try to mark tiles from dungeon 2 to dungeon 1. During kobolds are digging, with player 1, claim the tile in the way. The tile should not be marked anymore in player 2 screen and it should not be possible to mark it.
If you do the same with the multiplayer small 2v2 map, the claimed wall should be left marked and kobolds should dig it.
To test "kobolds can claim ennemy rooms", the most simple is to use the editor to build a room not too far from your dungeon :) Be careful of not doing it too near or your creatures will attack it