Sync base object code with Nova's

This brings Ironic's base object code more in line with nova's since the
time it was copied. There's still a large difference in the field/type
declarations that we should resolve at some point. (Would be helpful if
this was in oslo, maybe. :)

A couple of these changes are needed for my future patchsets for object
cleanup.

Change-Id: I7e233fb448e9ce56f707d230dc5b2558bdb0a1f9
Merge "Sync base object code with Nova's"