Update HACKING.rst with release note requirement

New patches to python-cinderclient must now add an entry for release
notes.

Change-Id: Id7fe24f2cabf4145933e0babc6641d250165ce74
Add assert to delete multiple test

Make sure calls are made to delete both volumes. Also removed redundant
fields in v1 fake volume.

Closes-Bug: #1253142
Change-Id: I51078041c6d765f28edb155d44928286ee2b0dd6
Merge "Update HACKING.rst with release note requirement"
Merge "Add assert to delete multiple test"