Camera: fix gfx undefined buffer issue

clear the render target before drawing, fix the undefined buffer
mess up issue of preview layer

Change-Id: I093fc0bdaf292fed2bc7f1a6d2678a94f25c9d55
CRs-fixed: 503216 506709
Gallery2: Fix show on map typo

Change-Id: I80cc825d3adf17fde9d245a71a4756f35bcd232f
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>