gv_stream: rework statistic counters.
gv_stream: rework statistic counters.

AravisProject/aravis,AnilRamachandran/aravis,lu-zero/aravis,AnilRamachandran/aravis,AnilRamachandran/aravis,lu-zero/aravis,lu-zero/aravis,AravisProject/aravis,lu-zero/aravis,AravisProject/aravis,AravisProject/aravis,AnilRamachandran/aravis,AnilRamachandran/aravis,lu-zero/aravis,AravisProject/aravis