Exception on subcloud admin address pool delete

[Lucas Ratusznei Fonseca]

Brief Description
-----------------

System AIO-SX (virtualbox) subcloud initially bootstrapped with the admin network.

When an admin address pool is deleted (system addrpool-delete), the expected behaviour is that a subcloud falls back to using the management network.

An exception is occurring when performing this activity after the integration of the L3 firewall feature:

https://opendev.org/starlingx/config/src/branch/master/sysinv/sysinv/sysinv/sysinv/puppet/platform_firewall.py#L150

In the above scenerio, mgmt and cluster-host are still on the loopback interface (as the admin network is handling communication to/from the system controller). So the only network in firewall_networks is the oam network. Thus, referencing the network dict for mgmt will cause an exception.

This code is currently contained in get_host_config(). This is called any time the puppet hieradata needs to get updated. That is, whenever a runtime manifest needs to go (this case), or other activities like host lock/unlock.

Severity
--------
Minor: System/Feature is usable with minor issue

Reproducibility
---------------
100% reproducible

[Ghada Khalil (gkhalil)]

Related to recent code changes for: https://storyboard.openstack.org/#!/story/2010591

Fixed by: https://review.opendev.org/c/starlingx/config/+/889125