Initialize base_q_ratio to a reasonable value

This prevents use-of-uninitialized-value when running under MSAN
in a downstream test.

Change-Id: I72dd8406820b5ce715279fc6aba7d233bb171675
diff --git a/av1/qmode_rc/ratectrl_qmode.cc b/av1/qmode_rc/ratectrl_qmode.cc
index 6556b60..888323b 100644
--- a/av1/qmode_rc/ratectrl_qmode.cc
+++ b/av1/qmode_rc/ratectrl_qmode.cc
@@ -179,6 +179,7 @@
   bool has_arf_frame = show_frame_count > kMinIntervalToAddArf;
 
   gop_struct.display_tracker = 0;
+  gop_struct.base_q_ratio = 1.0;
 
   GopFrame gop_frame;
   if (has_key_frame) {