Swap media direction check for `subscribe request`

as @rfuchs mentioned in his review, the SEND/RECV media flags are set
according to rtpengine's perspective, not the media flow's one.

daemon/call.c

@@ -2972,7 +2972,7 @@ static int monologue_subscribe_request1(struct call_monologue *src_ml, struct ca
 
 		codec_handlers_update(dst_media, src_media, flags, sp);
 
-		if (MEDIA_ISSET(src_media, SEND))
+		if (MEDIA_ISSET(src_media, RECV))
 			MEDIA_SET(dst_media, SEND);
 		else
 			MEDIA_CLEAR(dst_media, SEND);