fixing some naming and typo in transport-udt

[zazf]

Motivation:

I accidentally find some typos in the transport-udt module, and two of them actually can affect the correctness of execution.

Modification:

Only changed some variable namings.
Variables in some setters in DefaultUdtChannelConfig.java and DefaultUdtServerChannelConfig.java are named incorrectly.

Result:

Now, DefaultUdtChannelConfig won't set SystemReceiveBufferSize and SystemSendBufferSize incorrectly.

[normanmaurer]

@zazf can you sign our icla and let me know once done : https://netty.io/s/icla ?

[zazf]

@normanmaurer Signed

[normanmaurer]

@zazf Thanks!