need explicit way to say "do not poweroff"

[Scott Moser]

at https://gist.github.com/smoser/2610e9b78b8d7b54319675d9e3986a1 i suggested people do:
power_state: None

but that does not work, and exits non-true because handling power state raises a type error.

we should fix power_state: None to work
but should also provide an explicit way to say "do nothing".

[Scott Moser (smoser)]

marking this invalid.
power_state: null

is the correct way in yaml to declare 'None'. we do support it. i just have to update doc.

[Scott Moser (smoser)]

re-opened.
i woudl like to be able to do:

power_state:
  mode: no-poweroff

or some nice way of keeping the dictionary but explicitly saying "just stay up"