Fix some @hide usage in Tethering(Cont.)

Using alternative way to fix @hide usage. Do not have API change.

Bug: 144814072
Test: buid
Change-Id: Ia23e319ad3779318471d01cbfa17b8c6df4960d3

Tethering/src/android/net/ip/RouterAdvertisementDaemon.java

@@ -668,7 +668,7 @@ public class RouterAdvertisementDaemon {
     }
 
     private final class UnicastResponder extends Thread {
-        private final InetSocketAddress mSolicitor = new InetSocketAddress();
+        private final InetSocketAddress mSolicitor = new InetSocketAddress(0);
         // The recycled buffer for receiving Router Solicitations from clients.
         // If the RS is larger than IPV6_MIN_MTU the packets are truncated.
         // This is fine since currently only byte 0 is examined anyway.