1. Better explain the security groups / nsx security groups / firewall sections
admiun utilities.
2. Also remove the unrelated firewall sections reorder form the fix-mismatch utility
3. fix some warnings that appeared when runnin g the utilities
4. Add new utilities to list/clean unused NSX sections:
- List NSX firewall sections that does not have a matching neutron security group::
nsxadmin -r firewall-section -o list-unused
- Delete NSX firewall sections that does not have a matching neutron security group::
nsxadmin -r firewall-section -o nsx-clean
Change-Id: Ie9868d1fb196964ce479bca2c42d4a6eea7ef427
2825e30777