When running in a deployment that is focused on bundles rather
than a specific charm, the Octavia setup can fail because there
is no configured charm_name in the tests.yaml. This change
ensures that the Octavia setup can continue.
The current test code for octavia requires DVR extensions to be
present on the Neutron API server.
We need to conditionally enable this based on enabled extensions to
allow the test to operate on multiple deployment configurations.