use sub-resource API extension support
use sub-resource API extension support

Now that neutron-lib supports sub-resources [1], there's no need for
extension classes to override update_attributes_map and
get_extended_resources to add their own sub-resources. This patch
removes those methods from the qos extensions class.

NeutronLibImpact

[1] I8ae11633962a48de6e8559b85447b8c8c753d705

Change-Id: Ibb66246091fd84e18c56009f5fcb8fdea3aff6b7

mahak/neutron,openstack/neutron,openstack/neutron,huntxu/neutron,openstack/neutron,mahak/neutron,noironetworks/neutron,noironetworks/neutron,mahak/neutron,huntxu/neutron