New objects are children of NovaObject class. Such parent
will give us a good control of objects versioning. Also it
will force contributors to dump objects version in case of
any changes. These objects will be used to transmit data
via RPC. Old objects were used only for storing data.
During RPC transmission they are transform into dictionaries.
It is not right approach because we will have some problems
in case of adding new diagnostics fields.
Version of compute RPC was bumped.
Also some changes were made in libvirt driver method
get_instance_diagnostics(). These changes were made to fill
new fields of 'Diagnostics' object.
Implementation of method get_instance_diagnostics()
for other virt drivers will be changed in future patches.
blueprint: restore-vm-diagnostics
Change-Id: I5e2d116df045f803c654f7810b939b5fc859cfbf
a6335343cf