Undertow does not provide a way to check if data is available to read
but instead we have to try to read and see if any data is returned.
This makes it impossible to implement checkOnDataAvailable without
trying to read and that can lead to infinite recursion like this:
...
UndertowServerHttpRequest$RequestBodyPublisher.checkOnDataAvailable(UndertowServerHttpRequest.java:156)
AbstractListenerReadPublisher.changeToDemandState(AbstractListenerReadPublisher.java:177)
AbstractListenerReadPublisher.access$900(AbstractListenerReadPublisher.java:47)
AbstractListenerReadPublisher$State$4.onDataAvailable(AbstractListenerReadPublisher.java:319)
AbstractListenerReadPublisher.onDataAvailable(AbstractListenerReadPublisher.java:85)
UndertowServerHttpRequest$RequestBodyPublisher.checkOnDataAvailable(UndertowServerHttpRequest.java:156)
This commit prevent the call to checkOnDataAvailable() when switching
states from READING->DEMAND which implies we exited the readAndPublish
loop because there was no more data to read.
Issue: SPR-16545
f9df8c738a