retire gettor-01

in #40789 (closed) we moved gettor to rdsys-frontend, which makes this VM moot. start the retirement process in one week (e.g. turn off the VM in a week).

1. announcement (this ticket should be enough)
2. nagios
3. retire the host in fabric (in a week)
4. remove from LDAP with ldapvi
5. power-grep
6. remove from tor-passwords
7. remove from DNSwl
8. remove from docs
9. remove from racks
10. remove from reverse DNS
11. archive old gitolite repos (except gettor-web, see tpo/web/team#44 (closed))