Fix setsector not to disclose number of landmines to occupier

Fix setsector not to disclose number of landmines to occupier

When the deity sets the number of mines with setsector, the sector
owner (if any) is told the resulting number of mines.  Even for
occupied sectors, where mines belong to the old owner, and thus
shouldn't be disclosed.  Oops.

Fix setsector not to tell the sector owner anything then.