Make root hints consistent with authoritative data

Make root hints consistent with authoritative data

Resolvers in the "filter-aaaa" system test are configured with a single
root hint: "ns.rootservers.net", pointing to 10.53.0.1.  However,
querying ns1 for "ns.rootservers.net" results in NXDOMAIN answers.
Since the TTL for the root hint is set to 0, it may happen that a
resolver's ADB will be asked to return any known addresses for
"ns.rootservers.net", but it will only have access to a cached NXDOMAIN
answer for that name and an expired root hint, which will result in a
resolution failure, triggering a false positive for the "filter-aaaa"
system test.  Prevent this from happening by making all the root hints
consistent with authoritative data served by ns1.