actually use value of udp parameter

bin/hlsdump

@@ -50,7 +50,7 @@ if (hlsdump.sync)
   stream = stream.pipe(tslimit());
 
 if (hlsdump.udp)
-  stream.pipe(tsblast(1234));
+  stream.pipe(tsblast(hlsdump.udp));
 
 if (hlsdump.output) {
   var dst;