neutronv2: treat instance as object in deallocate_for_instance

The deallocate_for_instance method is given an instance object
but the neutronv2 API was treating it like a dict. This changes
the method to use dot notatoin for accessing fields on the
object and updates the unit tests to pass an instance object
rather than a dict.

Part of blueprint compute-manager-objects-juno

Change-Id: I784d1d59c23da8485d355251aba26b98bd9c7a16
Updated from global requirements

Change-Id: I07afee130b7e1a362597784e8e31dc35e6f74674
fix typo in docstring

Change-Id: Id89ddf8110ed63596f23fcabb2996fd0c0afe87f
Closes-Bug: #1359002
Merge "neutronv2: treat instance as object in deallocate_for_instance"
Merge "Updated from global requirements"
Merge "fix typo in docstring"