Use find_tile in get_tile so that tile microcache is properly updated

There is only one place in the code where find_tile_main_cache is called instead of calling find_tile. Not calling find_tile means that get_tile will not update the microcache.

This small change fixes that issue. Note that this does not really cause any problems besides a slightly stale microcache when get_tile is used.

Removed tile->use() too following Larry's indication.