Polonius fact generation: fix path access fact location

This will fix the other move errors false positives:
emitting the fact at the start point caused accesses to be at the
same point as an initialization fact of the return place of a call
on the following block, which emitted an error.

Author: lqd

src/librustc_mir/borrow_check/type_check/liveness/polonius.rs

@@ -43,7 +43,7 @@ impl UseFactsExtractor<'_> {
 
     fn insert_path_access(&mut self, path: MovePathIndex, location: Location) {
         debug!("UseFactsExtractor::insert_path_access({:?}, {:?})", path, location);
-        self.path_accessed_at_base.push((path, self.location_table.start_index(location)));
+        self.path_accessed_at_base.push((path, self.location_to_index(location)));
     }
 
     fn place_to_mpi(&self, place: &Place<'_>) -> Option<MovePathIndex> {