fix end call exponential stats bug
fix end call exponential stats bug

juxiangjun/webrtc-jingle-client,juxiangjun/webrtc-jingle-client,lukeweber/webrtc-jingle-client,zzhhui/webrtc-jingle-client,juxiangjun/webrtc-jingle-client,lukeweber/webrtc-jingle-client,lukeweber/webrtc-jingle-client,zzhhui/webrtc-jingle-client,juxiangjun/webrtc-jingle-client,fishwenHub/webrtc-jingle-client,lukeweber/webrtc-jingle-client,tempbottle/webrtc-jingle-client,tempbottle/webrtc-jingle-client,fishwenHub/webrtc-jingle-client,zzhhui/webrtc-jingle-client,tempbottle/webrtc-jingle-client,tempbottle/webrtc-jingle-client,zzhhui/webrtc-jingle-client,zzhhui/webrtc-jingle-client,juxiangjun/webrtc-jingle-client,lukeweber/webrtc-jingle-client,fishwenHub/webrtc-jingle-client,tempbottle/webrtc-jingle-client,fishwenHub/webrtc-jingle-client,fishwenHub/webrtc-jingle-client