Small optimization on audio IPC.

Check if we find the device before trying to define an interface,
so if we fail the if comparison plus the strdup are not necessary.
diff --git a/audio/unix.c b/audio/unix.c
index 23e2382..e0307e0 100644
--- a/audio/unix.c
+++ b/audio/unix.c
@@ -1257,14 +1257,13 @@
 	str2ba(req->source, &src);
 	str2ba(req->destination, &dst);
 
+	if (!manager_find_device(req->object, &src, &dst, NULL, FALSE))
+		goto failed;
+
 	if (req->transport == BT_CAPABILITIES_TRANSPORT_SCO)
 		client->interface = g_strdup(AUDIO_HEADSET_INTERFACE);
 	else if (req->transport == BT_CAPABILITIES_TRANSPORT_A2DP)
 		client->interface = g_strdup(AUDIO_SINK_INTERFACE);
-
-	if (!manager_find_device(req->object, &src, &dst, NULL, FALSE))
-		goto failed;
-
 	dev = manager_find_device(req->object, &src, &dst, client->interface,
 				TRUE);
 	if (!dev && (req->flags & BT_FLAG_AUTOCONNECT))