Correct reason for poor/lost score. (#3397)

No functional change, just logging reason was confusing.
Also, log no packets case. Seeing some instances in staging where there
are periods of no packets received. Trying to understand better.

pkg/sfu/connectionquality/scorer.go

@@ -408,10 +408,10 @@ func (q *qualityScorer) updateAtLocked(stat *windowStat, at time.Time) {
 	var score, packetScore, bitrateScore, layerScore float64
 	if stat.packets+stat.packetsPadding == 0 {
 		if !stat.lastRTCPAt.IsZero() && at.Sub(stat.lastRTCPAt) > stat.duration {
-			reason = "dry"
+			reason = "rtcp"
 			score = qualityTransitionScore[livekit.ConnectionQuality_LOST]
 		} else {
-			reason = "rtcp"
+			reason = "dry"
 			score = qualityTransitionScore[livekit.ConnectionQuality_POOR]
 		}
 	} else {

pkg/sfu/rtpstats/rtpstats_base.go

@@ -468,6 +468,13 @@ func (r *rtpStatsBase) deltaInfo(
 			StartTime: time.Unix(0, startTime),
 			EndTime:   time.Unix(0, endTime),
 		}
+		loggingFields = []interface{}{
+			"snapshotID", snapshotID,
+			"snapshotNow", now,
+			"snapshotThen", then,
+			"duration", time.Duration(endTime - startTime),
+		}
+		err = errors.New("no packets in delta")
 		return
 	}