What is this usage of harrumph?

Solution 1:

The Governor is running through a bombastic tirade about things that make him unhappy. His Harrumph fits both definitions.

He is surrounded by yes-men, lackeys of no particular viewpoint or individual strength. He expects each and every one of them to be echoing his every expression, including his every harrumph.

Solution 2:

While the official dictionary definition doesn't really agree with this, I always viewed this as the yes-men doing what yes-men do. Which is parroting and reinforcing the primary person's opinion without real thought of their own. The Governor says "harrumph" the yes-men say "harrumph." The governor actually uses it in the correct way, the yes-men parrot him. So they are agreeing with him by using a word that technically means they aren't. So in a way it is a subtle joke, among the many not so subtle jokes.