Don't use OpenDNS as the default resolvers

OpenDNS returns self referencing records instead of pure
NXDOMAIN records:

root@kevin-test-1:~# host kevin-test
kevin-test has address 67.215.65.132
Host kevin-test not found: 3(NXDOMAIN)

NetRange:       67.215.64.0 - 67.215.95.255
CIDR:           67.215.64.0/19
OriginAS:       AS36692
NetName:        OPENDNS-NET-3

Clearly this is not preferable when the server is being
used as an upstream resolver for internal DNS which may
send incorrectly configured applications running in VMs
to the wrong place

Change-Id: I098bb57e9e71fc3db5b3e4b3d42d9a3e1d966a04