Add a max condition and lower the min value.

No change in behavior (metrics for yt live set) for the
default min/max_gf_interval=4/16 settings.
Small positive change when min/max_gf_interval=7/16
(for 60fps clips on ytlive set).

Change-Id: I1c1d72425c86c69419ea43fb9730130e81062f91