Fix LinkProperties's equals() method.

LinkProperties's equals() method was broken by the addition of
stacked interfaces. The reason was that equals() was checking
the equality of mStackedInterfaces.keys(), which is just an
enumeration, instead of mStackedInterfaces.keySet(), which
actually contains the keys. The test was failing, but I didn't
notice.

Fix the bug and make the test check the objects more in depth
so it can give more detailed error messages when equals() fails.

Bug: 8276725
Change-Id: Ie990bd75f641c28e63e54d953dcd0f4de13f7c9f

core/java/android/net/LinkProperties.java

@@ -378,7 +378,7 @@ public class LinkProperties implements Parcelable {
      * @return {@code true} if both are identical, {@code false} otherwise.
      */
     public boolean isIdenticalStackedLinks(LinkProperties target) {
-        if (!mStackedLinks.keys().equals(target.mStackedLinks.keys())) {
+        if (!mStackedLinks.keySet().equals(target.mStackedLinks.keySet())) {
             return false;
         }
         for (LinkProperties stacked : mStackedLinks.values()) {