Register objects in more services

We should be making sure we're registering objects in the services that
use them. In patches that follow, we'll stop importing the specific
object modules under nova/objects/. Also, we should register objects
after the config has been parsed, logging setup, and things monkey
patched. Also, also, also: let's import all objects and put the imports
in alphabetical order.

Change-Id: I07f4584c43bd88960d543962a162cd1dd8dea09a
Merge "Register objects in more services"