retire chi-node-11

The machine, including the iDRAC BMC, has been unresponsive for a few days. This cluster is EOL anyway, so we move for retirement immediately.

1. announcement
2. nagios
3. retire the host in fabric
4. remove from LDAP with ldapvi
5. power-grep
6. remove from tor-passwords
7. remove from DNSwl n/a
8. remove from docs
9. remove from racks
10. remove from reverse DNS