Make discovery of version for KS catalog smarter.

Instead of relying on the configuration file for determining how
the catalog should be parsed, make it flexible by inspecting the
structure of the service catalog passed to it.

Fixes bug 1180486

Change-Id: I0c8caf4c8365bf25377ab3a249ac280d8add0f17
Always return a list from VolumeTableMixIn._get*

Returning None from these methods leads to TypeError
(None is not iterable)

Fixes: bug #1182075
Change-Id: Ia5f5fe78669bbaed599b7dd5cae1beb69bde7796
Merge "Make discovery of version for KS catalog smarter."
Merge "Always return a list from VolumeTableMixIn._get*"