delegate methods: fix single field case (IDEA-154698)

java/java-tests/testData/codeInsight/delegateMethods/afterSingleField.java

@@ -0,0 +1,10 @@
+class A {
+  void foo(){}
+}
+class Test{
+    public void foo() {
+        a.foo();
+    }
+
+    private A a;
+}

java/java-tests/testData/codeInsight/delegateMethods/beforeSingleField.java

@@ -0,0 +1,6 @@
+class A {
+  void foo(){}
+}
+class Test{
+  private A <caret>a;
+}