Periodically the turn coordinator is jammed all the way to one side.

Initialize _last_rate to 0 at start up to hopefully avoid this.

src/Instrumentation/turn_indicator.cxx

@@ -13,7 +13,8 @@
 #define RESPONSIVENESS 0.25
 
 
-TurnIndicator::TurnIndicator ()
+TurnIndicator::TurnIndicator () :
+    _last_rate(0)
 {
 }