tmcast: tx: TTL 2 -> 100

So that we clearly see problems if packets are looped wrongly.

namespace_demo/tmcast.py

@@ -31,7 +31,7 @@ def _udpsockfor(ipaddr): # -> (sk, isipv6)
 
 
 # mjoin_tx returns socket prepated to send/receive to/from multicast group:port.
-def mjoin_tx(group, port, ttl=2):
+def mjoin_tx(group, port, ttl=100):
     sk, ip6 = _udpsockfor(group)
 
     # set ttl and default destination address (for tx)