chg: dev: support multigraph for nidb for VIRLDEV-336
chg: dev: Simplify ANM->NIDB step
chg: dev: pep8
chg: dev: remove redundant IP formatting code (uses platform base instead)
chg: dev: modify handling of not set IP addresses
chg: dev: allow broadcast domains to be excluded from alloc

But still present in IPv4 graph - allows partial manual allocation such
as for L2tp_v3 tunnels for VIRLDEV-53