UCLOUDNG-1304: support vNIC hot attach

Includes three patches from Havana and fix to use it in Grizzly.
- https://review.openstack.org/#/c/53969/
- https://review.openstack.org/#/c/56504/
- https://review.openstack.org/#/c/57069/
- Grizzly fix: pass conductor_api instance to get_instance_nw_info() call