Fix network_cidrs when ManageNetworks: false
Fix network_cidrs when ManageNetworks: false

The legacy parameters (e.g InternalApiNetCidr) default to the new
network_data.yaml values.

When ManageNetworks: true the value of these parameters is then used to
create the network resources. The cidr attribute of the resources are
then used to build the network_cidrs output value resulting in the
correct list of cidrs.

However when Managenetworks: false the resources are not created so an
alternative approach is required. Currently only the values from
network_data.yaml are used. If the legacy parameters are being used in
a deployment this will result in the cidrs from the default
t-h-t/network_data.yaml instead of the values from the heat parameters.

This can result in live migration failure as the firewall subnet is
incorrect on compute nodes.

To resolve this we can just use the value from the legacy params to
build the cidr list when ManageNetworks: false. There is also an
unnecessary list_concat which can be removed.

Closes-bug: 1929470
Change-Id: Ibe5f9ec4dc32a6e8277e95032e608209a035cad5

openstack/tripleo-heat-templates,openstack/tripleo-heat-templates