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
Camera: zh-rTW translations

Change-Id: I5328cfb0b942f57a9db8a19579a3ca978efa71e2
Merge branch 'cm-10.1' into martincz