ff_vvc_frame_rpl uses the flags to detect whether a frame is in use.
Therefore, in the case of a CVSS AU (RASL/GDR with
NoOutputBeforeRecoveryFlag) with ph_non_ref_pic_flag = 1, the frame
would be freed before it is used. Fix this by always marking the
current frame with VVC_FRAME_FLAG_SHORT_REF, as is done by the HEVC
decoder.
Signed-off-by: Frank Plowman <post@frankplowman.com>