support Octavia for LB

[jichenjc]

/kind feature

Describe the solution you'd like
[A clear and concise description of what you want to happen.]
follow up of #401
we have Neutron LBaas v2 support only now, need support Octavia as well...

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

[hidekazuna]

I am trying this issue based on #401 .