Fix explosions when taking instances from containers in low Minmus orbit.

The problem here is that during the few frames where the part is not
completely initialized, its colliders can hit things they shouldn't.
At 150 m/s orbital speed this causes big problems.

To fix this, initialize the part as physicless at first, and disable
its colliders. The enabled property doesn't stop them from colliding
with other vessels for some reason, so deactivate the whole GameObject.