VM in rescue state must have a restricted set of actions

[OpenStack Infra]

https://review.openstack.org/109624
commit 82a13b30b8153ee4a282604fcfffd1a015365487
Author: Leandro I. Costantino <email address hidden>
Date: Mon May 19 19:58:47 2014 -0300

    VM in rescue state must have a restricted set of actions

    Right now it is possible to pause, suspend and stop a VM in state RESCUED,
    so after the state is changed, it's not possible to trigger unrescue anymore
    since the original state is lost.

    This patch remove vm_states.RESCUED as valid state from stop,
    pause and suspend actions.

    The vm_states devref is also updated to reflect this change including the
    current reboot flow.( vm_states.RESCUED cannot be rebooted as per
    today code)

    This is a backport of 8ff170dc95bf3101fe38a2624e941bfa3b7c1138 .

    DocImpact
    Closes-Bug: #1319182
    Co-Authored-By: Cyril Roelandt <email address hidden>
    Change-Id: I531dea5a5499bf93c24bea37850d562134dee281