Fixed updating the owned villages for replace_map.

This disown villages that no longer exist after the replacement.
Capturing villages at places now a village will be added later.

(Fixes bug #20468.)

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56264 75b3775d-3801-0410-9e12-e2e43121521d