Fix encode failure in 1-pass setting

Resolve the encode failure in 1-pass coding setting due to the
interaction with the new active reference frame system.

BUG=aomedia:2451

STATS_CHANGED

Change-Id: If4a17f4d2caddeae4ec0bc56330d30a90edfdfc2
diff --git a/av1/encoder/pass2_strategy.c b/av1/encoder/pass2_strategy.c
index 0ef696f..1c6a2ee 100644
--- a/av1/encoder/pass2_strategy.c
+++ b/av1/encoder/pass2_strategy.c
@@ -804,12 +804,6 @@
   rc->gfu_boost = DEFAULT_GF_BOOST;
   rc->constrained_gf_group =
       (rc->baseline_gf_interval >= rc->frames_to_key) ? 1 : 0;
-  const int use_alt_ref =
-      is_altref_enabled(cpi) &&
-      (rc->baseline_gf_interval < cpi->oxcf.lag_in_frames) &&
-      !(cpi->lookahead->sz < rc->baseline_gf_interval - 1) &&
-      (cpi->oxcf.gf_max_pyr_height > MIN_PYRAMID_LVL);
-  rc->source_alt_ref_pending = use_alt_ref;
 
   // Set up the structure of this Group-Of-Pictures (same as GF_GROUP)
   av1_gop_setup_structure(cpi, frame_params);