Fix calculations in GF only group case

Fix calculations in GF only group case

- Fix the number of frames considered in calculation of
  twopass active worst quality. For GF only group, frames
  considered should be one less than baseline gf interval
  accounting for the golden frame.
- Fix in calculation of normal_frames. As baseline gf
  interval includes the golden frame, the number of
  normal frames should be one less than baseline gf
  interval.

Change-Id: I6c0cd0a39db23586fc390a6fba5d7aebc0dfce08