Fix Thread-Safety in the SyslogToMapTransformer

Syslog-udp module is creating wrong timestamp fields (even another numeric fields are bad transformed)
Checking the output from Java Mission Control, we have seen that Spring Integration component udp-inbound-channel-adapter is used, and also DatagramPacketMessageMapper in method toMessage, and in here might be the problem in a concurrent environment, with different threads accessing some share variable.
Attatch a file, with the syslog entry sent in a loop, and different output obtained for the same entry.
We used a simple stream syslog-udp | file in a Spring XD single-node, and also failed in a distributed way.