shelve doesn't work on nova-cells environment

The compute_api shelve/unshelve methods expect an Instance object,
but cell is still passing the sqlalchemy form.
So adding shelve/unshelve to the list of methods that will receive an
Instance object when using nova-cell.

When shelving instance with nova-cell environment,
instance object needs to contain 'metadata' and 'info_cache'.
So fetching the same from databse and adding it to
instance object before calling shelve/unshelve methods.

Conflicts:
    nova/cells/messaging.py

Closes-Bug: #1338451
Change-Id: Ia31b33c9a1d347f15d3e0a67fa31ef6b25a7407a
(cherry picked from commit 9d4b49c542e2076c8a572d1e8c6d50e255efe087)
Read deleted instances during lifecycle events

This prevents us from failing to find the associated instance if
the lifecycle event happens after the instance has been deleted,
as in the case of a ... delete.

Change-Id: I819ddf8ff68edc407d7932bf43771c440f514f26
Closes-bug: #1304968
(cherry picked from commit 53ad788af6ced83bd9d6e58a25196a325d60fc4e)
Merge "shelve doesn't work on nova-cells environment" into stable/icehouse