Pleading guilty or no contest is always considered a conviction, whoever you're dealing with, unless it has since been expunged or pardoned.
It's the other cases like deferred adjudication or where it's dismissed after completing probation that the rest of society (i.e. everybody except USCIS) treats it as a non-conviction, but USCIS treats it as a conviction. I expect DoD would follow the standard that applies to citizens not dealing with the USCIS -- meaning it's not a conviction unless you pleaded guilty or no contest, or were explicitly found guilty by a judge or jury. But I have no idea how they treat expungements and pardons.