Fix the unhandled authentication message.

bug id: http://b/2991911

Change-Id: Iec86e3aee0fb12034ee25bc0e93fd575c1208a5f
diff --git a/services/java/com/android/server/sip/SipSessionGroup.java b/services/java/com/android/server/sip/SipSessionGroup.java
index a3bf3eb..5a742de 100644
--- a/services/java/com/android/server/sip/SipSessionGroup.java
+++ b/services/java/com/android/server/sip/SipSessionGroup.java
@@ -872,6 +872,7 @@
                     mPeerSessionDescription = extractContent(response);
                     establishCall();
                     return true;
+                case Response.UNAUTHORIZED:
                 case Response.PROXY_AUTHENTICATION_REQUIRED:
                     if (handleAuthentication(event)) {
                         addSipSession(this);