Fix respawn not working at all when suitable position was not found

The player should always be teleported away when they die and
we can still fall back to the engine spawning code.

mods/spawn/init.lua

@@ -135,6 +135,7 @@ local function on_spawn(player)
 	if success then
 		player:set_pos(spawn_pos)
 	end
+	return success
 end
 
 minetest.register_on_newplayer(function(player)
@@ -153,7 +154,5 @@ minetest.register_on_respawnplayer(function(player)
 		return
 	end
 
-	on_spawn(player)
-
-	return true
+	return on_spawn(player)
 end)