implement automatic deploy of octavia

Now when we deploy Octavia with Kolla, we need manually configure:

- network,
- certs,
- key,
- security group，
- images
- and so on

This bp will automate those.

for certs:
we will add a switch called "auto_generate_certs", this will generate certs for octavia， but default value is false.for productive environment， this is might not safe。

for network: we will implement neutron ovs driver and brctl driver.

for key: create a public and private key, and copy private key to all octavia worker nodes, and use public key to create a nova keypair

for flavor: this will be configurable at global.yaml

for Security group: creat two security-groups , one is used for amphora vm, other is used
for octavia worker node.

for amphora image: auto build image for centos or ubuntu, this is configurable

finally: we need update docs