Fix conditions used to recognize forward coded keyframe

The original condition caused the first key frame in the sequence
to be coded as lossless, which dramatically increased the bit rate.

Change-Id: I56bba11191f6aab7d302a0e499623a8090426ea6

av1/encoder/ratectrl.c

diff --git a/av1/encoder/ratectrl.c b/av1/encoder/ratectrl.c
index f5b3851..4ec7613 100644
--- a/av1/encoder/ratectrl.c
+++ b/av1/encoder/ratectrl.c
@@ -1010,7 +1010,7 @@
       active_best_quality = cq_level;
       active_worst_quality = cq_level;
     } else if (cm->current_frame.frame_type == KEY_FRAME &&
-               cpi->oxcf.fwd_kf_enabled) {
+               cm->show_frame == 0) {
       // Handle the special case for forward reference key frames.
       // Increase the boost because this keyframe is used as a forward and
       // backward reference.