For bhyveDomObjFromDomain, bhyveDomainLookupByUUID, and
bhyveDomainLookupByID let's return a locked and referenced
@vm object so that callers can then use the common and more
consistent virDomainObjEndAPI in order to handle cleanup rather
than needing to know that the returned object is locked and
calling virObjectUnlock.

The LookupByName already returns the ref counted and locked object,
so this will make things more consistent.

For bhyveDomainUndefine and bhyveDomainDestroy since the
virDomainObjListRemove will return an unlocked object, we need to
relock before making the EndAPI call.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>