Transitional state with leader type removed
Promise specifies two different proposal numbers

 1) The minimum to-be-accepted proposal number.

    Messages can be delayed, so the response to a
    Propose message must echo the instance and
    proposal numbers in the Propose message.

 2) The proposal number of any accepted value.

    If a value has already been accepted, then
    the proposal number from its associated past
    Fix message must be included.