SnapdragonCamera: Fix the preview thumbnail issue

When set the preview thumbnail imageView to visible, it used the
drawable resource in cache which was set since last time. That
caused we still could see the preview thumbnail though the bitmap
was invalid.

Clear the drawable resource in cache when the preview thumbnail
is invalid.

Change-Id: Id37620d32b8dff8dd3cad0f33da678b8709e6ee1
CRs-Fixed: 899905
1 file changed