The lowercase network names was hardcoded to 'external',
'internal_api' and 'storage_mgmt'. Use jinja to get the
network.name_lower value from network_data.yaml instead
so that users can customize the lowercase network name.
Handle service_net_map_replace in the jinja2 logic so that
service_net_map_replace works for both default networks and
custom networks.
Enables a user either to change 'name_lower' of a network
and overriding the ServiceNetMap accordingly, as well as
user changeing 'name_lower' and use 'service_net_map_replace'
so that the default ServiceNetMap can be used.
Closes-Bug: #1830852
Change-Id: Ie9bd482782ff770d90dfc38a585237812ed81c06
(cherry picked from commit c0fcf8674d5f7c5c0cec1179fa56ef4536d5c5fb)
(cherry picked from commit f708ab7a827cc0db211b4709447f77126087347e)
c1865bafb1