[AnerleyEContactItem] Always re-set the avatar icon on disk
[AnerleyEContactItem] Always re-set the avatar icon on disk

With avatars generated from inline data we have to regenerate the on-disk file
each time the avatar has changed since we have no way in knowing if the avatar
data has changer or any other part has changed.

Fixes: MB#5371

meego-netbook-ux/anerley,meego-netbook-ux/anerley