IR: handle conflicts in resolveFakeOverride()

compiler/testData/codegen/box/traits/multipleImplFromJava.kt

@@ -0,0 +1,20 @@
+// TARGET_BACKEND: JVM
+// SKIP_JDK6
+// FILE: I.java
+interface I {
+    default String ifun() { return "fail"; }
+}
+
+// FILE: Z.java
+public class Z {
+    public String ifun() { return "OK"; }
+}
+
+// FILE: Zz.java
+public class Zz extends Z implements I {}
+
+// FILE: multipleImplFromJava.kt
+
+class Cc : Zz()
+
+fun box(): String = Zz().ifun()