Hard coded DHCP DNS options

[rcgoodfellow]

This line is causing problems and needs to be parameterized with the rack configured dns addresses.

opte/lib/oxide-vpc/src/engine/gateway/dhcp.rs

Line 84 in e5423d8

dns_servers: Some([Some(Ipv4Addr::from([8, 8, 8, 8])), None, None]),

[askfongjojo]

See also oxidecomputer/omicron#2153