What happens when a non-creature receives "+1/+1 until end of turn" effects, then later becomes a creature?
Thinking about it in a regular usage scenario, doesn't the vehicle get the +1/+1 effect before becoming a creature? 

When you tap the Veteran to crew, isn't the stack:


Vehicle gets +1/+1
Vehicle becomes a creature.


So, the vehicle gets +1/+1 before becoming a creature, but the effect applies after becoming a creature. In fact, there's never a point in time where it is a creature without the +1/+1.