Add configurable options for HA networks

Add configurable options for HA networks

The L3 HA mechanism creates a project network for HA (VRRP) traffic
among routers. The HA project network uses the first (default) network
type in 'tenant_network_types'. Depending on the environment, this
combination may not provide a desirable path for HA traffic. For
example, some operators may prefer to use a specific network for HA
traffic to prevent split-brain issues.

This patch adds configurable options that target the network_type and
the physical_network of the created HA network.

Doc-Impact
Closes-Bug: #1481443
Change-Id: I3527a780179b5982d6e0eb0b8c32d6dafeeab730