Set correct default values for some attributes
Set correct default values for some attributes

The specs says the default value for auto-aggregate should be False.

This change also changes default values from None to [] for import-rts,
export-rts and route-distinguishers, which is more cosmetic.

Closes-Bug: 1497209
Change-Id: I9a453382f89436beb67f74db392eaedaaba84526

openstack/networking-bgpvpn,openstack/networking-bgpvpn,openstack/networking-bgpvpn