extract super class: check for conflicts under progress; skip check for superclass inheritors mismatch - as no actual members would go there

java/java-tests/testData/refactoring/extractSuperClass/conflictUsingPrivateMethod/after/Test.java

@@ -0,0 +1,5 @@
+public class Test {
+    void x() {
+      foo();
+    }
+}

java/java-tests/testData/refactoring/extractSuperClass/conflictUsingPrivateMethod/after/TestSubclass.java

@@ -0,0 +1,4 @@
+public class TestSubclass extends Test {
+
+    private void foo(){}
+}