intrabc: adapt use_intrabc prob

First keyframe BD-RATE objective-1-fast:
   PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
-0.3705 | -0.3232 | -0.3812 |  -0.3782 |     N/A | -0.3412 |        N/A

First keyframe BD-RATE twitch-1:
   PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
-0.2479 | -0.2477 | -0.2467 |  -0.2567 | -0.2486 | -0.2508 |    -0.2487



Change-Id: Iea6c895c6fe9e9764887a8968f6e5330903969d3
diff --git a/av1/common/entropymode.c b/av1/common/entropymode.c
index e60c651..1d61e8e 100644
--- a/av1/common/entropymode.c
+++ b/av1/common/entropymode.c
@@ -4535,6 +4535,9 @@
 #if CONFIG_CFL
   av1_copy(fc->cfl_alpha_cdf, default_cfl_alpha_cdf);
 #endif
+#if CONFIG_INTRABC
+  fc->intrabc_prob = INTRABC_PROB_DEFAULT;
+#endif
 }
 
 int av1_switchable_interp_ind[SWITCHABLE_FILTERS];