Store net.Addr in clientIDAddrMap

This fixes a stats collection bug where we were converting client
addresses between a string and net.Addr using the clientAddr function
multiple times, resulting in an empty string for all addresses.

server/lib/snowflake.go

@@ -181,7 +181,7 @@ func (l *SnowflakeListener) acceptStreams(conn *kcp.UDPSession) error {
 			}
 			return err
 		}
-		l.QueueConn(&SnowflakeClientConn{Conn: stream, address: clientAddr(addr)})
+		l.QueueConn(&SnowflakeClientConn{Conn: stream, address: addr})
 	}
 }