Don't create networks if neutron is not enabled
Don't create networks if neutron is not enabled

With the composable undercloud installer, it's possible to disable
services.  The extraconfig script assumes both, neutron and nova, are
installed and fails if they aren't.

This patch checks if those services are available before.

Change-Id: Idcc2b9809fcfa92649a0a1f45175ce417dc0e608

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