fix the mess thumbnail when export 1080p/720p video to 848x480 resolution

Root cause: After export the video, the output frame size will be rewrote by the export
resolution, when rotate the phone, the frame will use the export resolution to display
which causes the mess thumbnail.
Fix: store the old output frame size and reset the size after export.

Change-Id: I05b6b6a87187969213fb9e44d95e7e0df2f06afa
Author: Wangyi Gu <wangyi.gu@intel.com>
Signed-off-by: Wangyi Gu <wangyi.gu@intel.com>
Signed-off-by: Tong, Bo <box.tong@intel.com>
Signed-off-by: Shuo Gao <shuo.gao@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 32193