Remove redundant whitelist for DHCP agent

It looks like the whitelist for the DHCP agent is added
twice. This looks like a genuine typo, and if it isn't
there is clearly something wrong! There's no good reason
for duplicating the list of whitelisted errors.

Change-Id: Ib94f60e8aa3ce1b0a6e28d9051da0124d403bf27
Merge "Remove redundant whitelist for DHCP agent"