Add a 'is_filter' keyword for each resource's attribute that can be
used as filter. In the future, we will rely on this to perform
filter validation: https://review.openstack.org/#/c/554368/ .
This patch processes the following resources: ports, segments,
trunks, address scopes, floating IPs, routers, subnetpools,
subnets, agents, availability zones, flavors, log, metering,
qos related resources.
Note: This patch processes the attributes that are documented
as filter parameter in api-ref.
Change-Id: I595b27a83fb2c185a4889030d619ce4d877fa881
Related-Bug: #1749820
eb27424cb0