A property x is 'self-promoting' if it is reliably the case that performing an action with a higher x-ness rating increases the expected aggregate x-ness of future actions.
This seems to be entirely your invention? I can't find any google results with a similar match.
Based on the title "Some Thoughts on Virtue Ethics for AIs" I'm assuming this is just a formalization of virtue ethics's idea of moral habituation. For example, from Aristotle's Nicomachean Ethics:
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