complete statement should add body to private interface methods (jdk9)

java/java-tests/testData/codeInsight/completeStatement/PrivateInterfaceMethodBody.java

@@ -0,0 +1,3 @@
+public interface Foo {
+    private void foo(<caret>)
+}

java/java-tests/testData/codeInsight/completeStatement/PrivateInterfaceMethodBody_after.java

@@ -0,0 +1,5 @@
+public interface Foo {
+    private void foo() {
+        <caret>
+    }
+}