telephony-ofono: fix resetting network status and signal

This prevent using status and signal from previous active modem
diff --git a/audio/telephony-ofono.c b/audio/telephony-ofono.c
index bc8fea2..0a7f0bd 100644
--- a/audio/telephony-ofono.c
+++ b/audio/telephony-ofono.c
@@ -1042,6 +1042,8 @@
 
 	g_free(net.operator_name);
 	net.operator_name = NULL;
+	net.status = NETWORK_REG_STATUS_NOSERV;
+	net.signals_bar = 0;
 
 	g_free(modem_obj_path);
 	modem_obj_path = NULL;