validate: avoid DNSSEC_NODS for . DS queries

... after the parent commit. Perhaps it can't cause trouble,
but I'll feel safer this way.
18 jobs for <span class="ref-name">marek/fix-servfails-for-root-ds</span> in 8 minutes and 15 seconds (queued for 12 seconds)
Status Job ID Name Coverage
  Build
passed #129176
docker linux amd64
build:clang:linux:amd64

00:00:58

passed #129175
docker linux amd64
build:linux:amd64

00:01:04

passed #129177
docker linux amd64 allowed to fail
srpm

00:01:07

 
  Test
passed #129184
docker linux amd64
deckard:linux:amd64

00:06:03

passed #129191
privileged
distro:epel-7

00:04:47

passed #129190
privileged
distro:fedora-27

00:05:05

passed #129183
docker
doc

00:00:39

passed #129182
docker linux amd64
installcheck:linux:amd64

00:01:31

passed #129185
docker linux amd64
installcheck:valgrind:linux:amd64

00:01:34

passed #129179
docker
lint:c

00:03:13

failed #129180
docker allowed to fail
lint:clang-scan-build

00:01:52

passed #129178
docker
lint:lua

00:00:52

passed #129188
docker linux amd64
respdiff:iter:tcp:linux:amd64

00:02:34

passed #129189
docker linux amd64
respdiff:iter:tls:linux:amd64

00:02:43

passed #129187
docker linux amd64
respdiff:iter:udp:linux:amd64

00:02:31

passed #129181
docker linux amd64
test:linux:amd64

00:02:38

passed #129186
docker linux amd64
test:linux:amd64:valgrind

00:01:14

 
  Coverage
passed #129192
docker linux amd64
coverage

00:00:31

71.6%
 
Name Stage Failure
failed
lint:clang-scan-build Test
  CCLD	modules/hints/hints.so
CCLD modules/stats/stats.so
CCLD modules/cookies/cookies.so
scan-build: 28 bugs found.
scan-build: Run 'scan-view /builds/knot/knot-resolver/scan-results/2018-04-12-101732-13-1' to examine bug reports.
Uploading artifacts...
scan-results: found 33 matching files
Uploading artifacts to coordinator... ok id=129180 responseStatus=201 Created token=icuTYuLx
ERROR: Job failed: exit code 1