do not flag dead code if custom JUnit runner is used (IDEA-25444)

java/java-tests/testData/inspection/deadCode/singleton/src/Main.java

@@ -0,0 +1,5 @@
+public class Main {
+   public static void main(String args[]) {
+      Singleton.getInstance();
+   }
+}

java/java-tests/testData/inspection/deadCode/singleton/src/Singleton.java

@@ -0,0 +1,7 @@
+pubic class Singleton {
+   private static Singleton ourInstance = new Singleton();
+
+   public Singleton getInstance() {
+      return ourInstance;
+   }
+}