Handle the hardcoded configuration values

This patch allows to customize the hardcoded configuration values,
as well as introduce new configuration options for designate services
by configmap template with the specified section:

  designate:
    server:
      configmap:
        DEFAULT:
          default_soa_refresh_min: 3500
          default_soa_refresh_max: 3600
          default_soa_minimum: 3600
        'network_api:neutron':
          admin_username: admin
          admin_password: password
          admin_tenant_name: tenant1

Change-Id: I43224d260bed265b21c748abe294c0a97bfb7f32
Related-Prod: PROD-29626
15 files changed