Adjutants aren't exactly Cerberus troops but rather Cerberus experiments. They aren't under the direct control of Cerberus. But Cerberus, or rather the Illusive Man, used them as a distraction so he could take over Omega. They let the "wild animals" loose and direct their efforts by offering paths of least resistance.
(More back story: http://masseffect.wikia.com/wiki/Mass_Effect:_Invasion)