Rename MANAGED to MANAGEABLE
Rename MANAGED to MANAGEABLE

The spec says that states ending with -ING and -ED are active states
(momentary, states that don't need a API call to transition from). The
only exception is the MANAGED state which is a passive state (a state that
needs an API call to transition from). This patch is renaming MANAGED
to MANAGEABLE to get rid of that exception and make naming more consistent
in the new state machine.

Change-Id: I7224c18d6a1afa063249232496f6e34729d7b794

bcornec/ironic-specs,NaohiroTamura/ironic-specs,naterh/ironic-specs,openstack/ironic-specs