#298 Fix multicast with -P > 1

[Robert McMahon]

Double check that the single stream multicast is no longer a requirement. Remove the message if so.

[root@ctrl1fc35 ~]# iperf -s -B 239.1.1.1%eno1 -u 
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Server listening on UDP port 5001
Joining multicast (*,G)=*,239.1.1.1 w/iface eno1
Server set to single client traffic mode (per multicast receive)
UDP buffer size:  208 KByte (default)
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