Support query filtering for cluster objects

The cluster_get_all implementation already supports query
parameters internally, but it is not exposed to the UI. Allow
query params to be passed in from the UI. Suppress an exception
when invalid filter fields are used, simply return empty list.
This will be a model for adding filtering to all x_list() methods
in the API.

Partial-implements: blueprint enable-result-filtering
Change-Id: I20a0de3056bb17cee2d55d87a61b2e23b9c4b657
Merge "Support query filtering for cluster objects"