Open Stack

Hi!

While working on the enroll spec [1], I got a thinking: within the new 
state machine, when should we allow to change a node driver?

My initial idea was to only allow driver change in ENROLL. Which sounds 
good to me, but then it will be impossible to change a driver after 
moving forward: we don't plan on having a way back to ENROLL from 
MANAGEABLE.

What do you folks think we should do:
1. Leave driver field as it was before
2. Allow changing driver in ENROLL, do not allow later
3. Allow changing driver in ENROLL only, but create a way back from 
MANAGEABLE to ENROLL ("unmanage"??)

Cheers,
Dmitry

[1] https://review.openstack.org/#/c/179151