prediction: add obstacle priority to obstacle history map.
prediction: add obstacle priority to obstacle history map.

Change-Id: I248e31805fabfdee29b44eccde3b5c47619f2910

ApolloAuto/apollo,ycool/apollo,ApolloAuto/apollo,ApolloAuto/apollo,ApolloAuto/apollo,ycool/apollo,ApolloAuto/apollo,ycool/apollo,ApolloAuto/apollo,ycool/apollo,ycool/apollo,ycool/apollo