Fix default argument method calls

In some cases, calls of methods with default arguments were invoked via the
actual generated method, not via the "...$default" accessor

compiler/testData/codegen/box/defaultArguments/function/contains.kt

@@ -0,0 +1,5 @@
+class A
+
+fun A.contains(i: A, actual: Boolean = true) = actual
+
+fun box() = if (A() in A()) "OK" else "Fail"