[4.0] clear cache when locale is changed

[4.0] clear cache when locale is changed

When locale is change, font configuration might provide a different font
list.

In this case, original cached font might not be valid for same script.
Therefore, we need to clear caches.

Change-Id: I5ba9a2aadbdf34e246fd1241d8257fa702409bbe
Signed-off-by: minho.sun <minho.sun@samsung.com>