Removes message receive code from NetworkSender, as it's useless

The removed code also, sometimes and for so far unknown reasons, would
 trigger on messages received from self and throw ClassCastExceptions
 as the payload would not be a Message but a HeapBuffer.
Merge pull request #3291 from digitalstain/2.2-remove-sender-receive

[2.2] Removes message receive code from NetworkSender, as it's useless