SipService: deliver connectivity change to all sessions.

+ add DATA_CONNECTION_LOST to SipErrorCode
+ convert it to Connection.DisconnectCause.LOST_SIGNAL in SipPhone

http://b/issue?id=2992548

Change-Id: Ie8983c1b81077b21f46304cf60b8e61df1ffd241

services/java/com/android/server/sip/SipService.java

@@ -404,6 +404,7 @@ public final class SipService extends ISipService.Stub {
 
         public void onConnectivityChanged(boolean connected)
                 throws SipException {
+            mSipGroup.onConnectivityChanged();
             if (connected) {
                 resetGroup(mLocalIp);
                 if (mOpened) openToReceiveCalls();