Make root hints consistent with authoritative data

Resolvers in the "filter-aaaa" system test are configured with a single
root hint: "", pointing to  However,
querying ns1 for "" 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
"", 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.

(cherry picked from commit c19ebde1)
48 jobs for !2206 with michal/filter-aaaa-system-test-make-root-hints-consistent-with-authoritative-data-v9_11 in 16 minutes (queued for 3 seconds)