Summary:
In elm_map_overlay_show and elm_map_overlays_show,
it frees overlays list members. This lists are used
in elm_map_overlay functions, so should remain.
Test Plan:
1. Run elementary_test -> Geographic -> Map
2. Click group overlay (whose text is "3") -> bubble appears
3. Click "Show" button -> observe no more Eina Magic Check Failure appear.
Reviewers: jpeg, cedric, woohyun
Differential Revision: https://phab.enlightenment.org/D5191