You can also turn off healthbars for a unit using the following method, however this way you will also turn off the ability to select the unit.
1) Using triggers add the 'locust' ability to your unit whenever it is made. You mighty have to use custom script use something like this call UnitAddAbilityBJ( 'Aloc', GetLastCreatedUnit() ).
2) Create a custom ability based off the 'chaos' ability and set the unit for it which you want. Note the unit of the chaos ability must be different from your created unit. Add this ability using triggers to the unit as well after the locust ability.
You will get an unselectable unit (the unit itself will be the one which is in the chaos ability) which doesn't show healthbars at all. The unit still can be attacked and can still auto-target or receive orders by triggers and has collision.