Fix InstanceNotFound error in _delete_instance_files

Currently the cleanup_running_deleted_instances peroidic task
failed with InstanceNotFound exception, this is because the
db query is not including the deleted instance while
_delete_instance_files() in libvirt driver.

Closes-bug: #1280140

Change-Id: Ie65ff255ad3c582a71db93b07304a21d4976a193
Clean up _make_*_list in object models to use base.obj_make_list

There are a lot of places where _make_foo_list()s are implemented.
Actually base.obj_make_list() can be used to make the list.

The patch is to clean up the redundancies and make the code clean.

Also, in order to make _from_db_objects()s the same format, we add
'context' into the parameter list in instance fault object.

Related to blueprint icehouse-objects.

Change-Id: I1a68b6e9dc402d4e30a06f94b068233e2afa713f
Merge "Fix InstanceNotFound error in _delete_instance_files"
Merge "Clean up _make_*_list in object models to use base.obj_make_list"