nsrep: allow inclusion of good nameservers if there's space in selection

The current algorithm doesn't work if there's 3 unknown nameservers in the
address selection set, and the 4th is known working with higher score
than unknown.
54 jobs for <span class="ref-name">nsrep-bugfix</span> in 10 minutes and 51 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Build
passed #246426
docker linux amd64
archive

00:00:56

passed #246427
docker linux amd64
build

00:01:00

passed #246428
docker linux amd64
build-asan

00:01:01

passed #246429
docker
kres-gen

00:00:59

canceled #246359
docker linux amd64
archive

00:00:05

canceled #246360
docker linux amd64
build

00:00:05

canceled #246361
docker linux amd64
build-asan

00:00:05

canceled #246362
docker
kres-gen

00:00:05

 
  Test
passed #246430
docker delayed
build:darwin

00:00:23

passed #246431
docker linux amd64
deckard

00:01:50

passed #246432
docker delayed
doc

00:00:47

passed #246433
dind
docker

00:02:57

passed #246434
docker delayed
lint:other

00:00:44

passed #246435
docker linux amd64 delayed
lint:pedantic

00:01:00

passed #246436
docker linux amd64
lint:scan-build

00:02:35

passed #246437
docker linux amd64
lint:tidy

00:02:41

passed #246438
privileged
pkg:epel-7

00:02:32

passed #246439
privileged
pkg:fedora-29

00:03:15

passed #246440
docker linux amd64
respdiff:basic

00:04:46

passed #246441
docker linux amd64 delayed
test:valgrind

00:01:34

canceled #246363
docker delayed
build:darwin

canceled #246364
docker linux amd64
deckard

canceled #246365
docker delayed
doc

canceled #246366
dind
docker

canceled #246367
docker delayed
lint:other

canceled #246368
docker linux amd64 delayed
lint:pedantic

canceled #246369
docker linux amd64
lint:scan-build

canceled #246370
docker linux amd64
lint:tidy

canceled #246371
privileged
pkg:epel-7

canceled #246372
privileged
pkg:fedora-29

canceled #246373
docker linux amd64
respdiff:basic

canceled #246374
docker linux amd64 delayed
test:valgrind

 
  Extended
canceled #246443
respdiff
fwd-tls6-kresd.udp6

canceled #246444
respdiff
fwd-udp6-kresd.udp6

canceled #246448
respdiff
fwd-udp6-unbound.tcp6

canceled #246449
respdiff
fwd-udp6-unbound.tls6

canceled #246447
respdiff
fwd-udp6-unbound.udp6

canceled #246446
respdiff
iter.tls6

canceled #246445
respdiff
iter.udp6

passed #246442
docker linux amd64
pytests

00:05:03

canceled #246450
respdiff
resperf:fwd-tls6.udp-asan

canceled #246451
respdiff
resperf:fwd-udp6.udp-asan

canceled #246452
respdiff
resperf:iter.udp-asan

canceled #246376
respdiff
fwd-tls6-kresd.udp6

canceled #246377
respdiff
fwd-udp6-kresd.udp6

canceled #246381
respdiff
fwd-udp6-unbound.tcp6

canceled #246382
respdiff
fwd-udp6-unbound.tls6

canceled #246380
respdiff
fwd-udp6-unbound.udp6

canceled #246379
respdiff
iter.tls6

canceled #246378
respdiff
iter.udp6

canceled #246375
docker linux amd64
pytests

canceled #246383
respdiff
resperf:fwd-tls6.udp-asan

canceled #246384
respdiff
resperf:fwd-udp6.udp-asan

canceled #246385
respdiff
resperf:iter.udp-asan