core: fix connection updated/removed signal handling

The DBusGProxy was getting destroyed after all the ListConnections calls
were completed, and thus the dbus match was removed, and the signals
weren't getting reflected back up into NM to be handled.  Fix that by
attaching the DBusGProxy to the NMConnection it represents to ensure it
lives until that NMConnection dies.

src/nm-manager.c

@@ -630,6 +630,16 @@ user_connection_get_settings_cb  (DBusGProxy *proxy,
 			                     g_strdup (path),
 			                     connection);
 			existing = NULL;
+
+			/* Attach the D-Bus proxy representing the remote NMConnection
+			 * to the local NMConnection object to ensure it stays alive to
+			 * continue delivering signals.  It'll be destroyed once the
+			 * NMConnection is destroyed.
+			 */
+			g_object_set_data_full (G_OBJECT (connection),
+			                        "proxy",
+			                        info->proxy,
+			                        g_object_ref (info->proxy));
 		} else
 			g_object_unref (connection);