Fix TetheredClient and TetheredClientTest

- Ensure that addAddresses preserves the ordering of addresses
 - Fix assertion that was supposed to check equality of TetheredClient
   with a different tethering type, and used the same type.

Bug: 148996181
Test: atest TetheringTests
Change-Id: I86cef7b834d7ae7afa3d1d748ccac6b3a7e57ebc

Tethering/common/TetheringLib/src/android/net/TetheredClient.java

@@ -25,7 +25,7 @@ import android.os.Parcelable;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Objects;
 
@@ -83,7 +83,7 @@ public final class TetheredClient implements Parcelable {
      * @hide
      */
     public TetheredClient addAddresses(@NonNull TetheredClient other) {
-        final HashSet<AddressInfo> newAddresses = new HashSet<>(
+        final LinkedHashSet<AddressInfo> newAddresses = new LinkedHashSet<>(
                 mAddresses.size() + other.mAddresses.size());
         newAddresses.addAll(mAddresses);
         newAddresses.addAll(other.mAddresses);