You need to use 2 units.
The first unit has no attack.
The second unit has an attack, barrage (to give multishot), Locust (to make it unclickable), Invulnerable, and no model.
You'll need a few triggers to handle this:
1. When the kodo is trained, you create the attacker unit and link them together using either a unit indexer or a hashtable.
2. Make a looping trigger that moves the attacker unit to the position of the kodo using the custom script SetUnitX/SetUnitY.
3. When the kodo dies, kill its associated attacker unit.