C#: Exhaustive validation of postupdate notes in conditional expression example.

Author: michaelnebel

csharp/ql/test/library-tests/dataflow/global/GlobalDataFlow.cs

@@ -506,12 +506,15 @@ public void M6(bool b1, bool b2, bool b3)
         var x2 = new SimpleClass();
         TaintField(b1 ? x1 : x2);
         Check(x1.field);
+        Check(x2.field);
 
         var y1 = new SimpleClass();
         var y2 = new SimpleClass();
         var y3 = new SimpleClass();
         TaintField(b2 ? (b3 ? y1 : y2) : y3);
+        Check(y1.field);
         Check(y2.field);
+        Check(y3.field);
     }
 
     private class SubSimpleClass : SimpleClass { }