Modify active_worst_quality setting for one pass CBR.
Current setting had active_worst_quality set too high (close to worst_quality) for first frame(s) following first key frame. This changes that to be somewhat more aggressive in allowing active_worst_quality to be lower following key frame. Also remove the 4/5 reduction in active_worst for key frame as this should be set by the user qp_max setting. Change-Id: I0530b3ddcc85c00e3eb7568de1b14a31206c4a4c