Fix crash on resolution change (issue 2393).

Don't free RBSP tables (containing decoded NAL units) on resolution
change, because we actually need this data to decode the frame after
reiniting (with new resolution). Fixed issue 2393.

Signed-off-by: Janne Grunau <janne-ffmpeg@jannau.net>
(cherry picked from commit 9107892624c8f9978489ab5b4c0ef2fc5637fb62)
