Camera: change to fix camera preview stretched issue

When change camera preview size between 16:9 and 4:3, we need update
the CamereScreenNail size, but this size will never update the size
of mRenderWidth and mRenderHeight, this cause the function getWidth
and getHeight get a wrong size, and cause the camera preview stretched
change the method to fix this issue.

CRs-Fixed: 507577

Change-Id: I00744851e0ecc393b13e907423ac6ec27230ff49