add source url to gStream2tcp script

var/local/xcache/gStream2tcp.py

 #!/usr/bin/env python3.6
 
+# from https://github.com/ivukotic/docker-xcache/blob/40d6fee1b49742ff58f06067f153f95c8fc6171f/atlas-xcache/gStream2tcp.py
+
 # this code runs in a reporter container listens for gStream monitoring packets
 # decodes them, resends as TCP packets