vp9: Fix to active_best for GF/ARF in 1 pass vbr.

Correct the setting of Q basis of GF/ARF in 1 pass vbr.

Existing logic would switch to using avg_QP of key frame if
avg_QP of inter is less than active worst (even if key frame is
not last frame).

Instead fix the logic (as per the comment) to use the lower of
active_worst_quality and avg_Q for inter as basis for GF/ARF
active_best_quality (unless last frame was key frame).

Increase in metrics: AvgPSNR/SSIM up by ~0.7/0.3 on ytlive set.

Change-Id: I9a628378ec6684bfda9457ebfc2384ef6d8579f7

vp9/encoder/vp9_ratectrl.c

@@ -882,9 +882,12 @@ static int rc_pick_q_and_bounds_one_pass_vbr(const VP9_COMP *cpi,
     // Use the lower of active_worst_quality and recent
     // average Q as basis for GF/ARF best Q limit unless last frame was
     // a key frame.
-    if (rc->frames_since_key > 1 &&
-        rc->avg_frame_qindex[INTER_FRAME] < active_worst_quality) {
-      q = rc->avg_frame_qindex[INTER_FRAME];
+    if (rc->frames_since_key > 1) {
+      if (rc->avg_frame_qindex[INTER_FRAME] < active_worst_quality) {
+        q = rc->avg_frame_qindex[INTER_FRAME];
+      } else {
+        q = active_worst_quality;
+      }
     } else {
       q = rc->avg_frame_qindex[KEY_FRAME];
     }