Using divert suffers the same context ambiguity – divert implies that the dog should have been attending to the passerby, and returning to the walk at hand is the diversion from the proper focus of attention. This might indeed be the intended meaning – that the dog should pay attention, briefly, to passersby, then on command accept and disregard the momentary change in focus of attention.

Avert, though, fails whatever the trainer intended to say.