I'd say in this instance that the 'race' of the Aussies the term is directed at in this context is white. As such, you'd need to argue that the term 'convict' is racist to all whites across the globe to qualify as racism. It obviously isn't as it's specifically used in the context of Australians. Therefore, the definition of xenophobia (prejudice against people of other countries) is more applicable.
Racism specific to skin colour, xenophobia more for an attack on specific nationalities.
Just to add, I'm a bit of cricket nut and have attended plenty of games against the Aussies. They don't take the term to heart at all in my experience. It's taken in good spirits. I've also heard them come out with far worse about the English ! There's a love/hate relationship between Aussies and the English. They pretend to hate us but they don't and all generally enjoy the banter, certainly more so at the cricket than the rugby.
Just my view.