remove decom'ed hosts from DHCP

removes gilman, palladium, strontium and alsted

per the report on:
RT #6123

..unless they're here to be
reinstalled with the same name..

please confirm they're gone for real,
the're all not in DNS anymore

Change-Id: Ib6b1328cea3b82fc2e3b996e09177e5c82b26ca0
Merge "remove decom'ed hosts from DHCP" into production