fix hangs caused by redoPlacement

After parsing a tile, it redoes placement for that tile if the angle has
changed since it started parsing. These redo calls were accidentally
done from the worker thread. Assigning the new work to `workRequest`
caused it to cancel itself.

Fix the problem by calling redoPlacement from the map thread.

src/mbgl/map/vector_tile_data.cpp

@@ -64,7 +64,6 @@ void VectorTileData::parse() {
             setState(State::partial);
         } else {
             setState(State::parsed);
-            redoPlacement();
         }
     } catch (const std::exception& ex) {
         std::stringstream message;