http: fix parallel execution of HTTP tests with SO_REUSEPORT

We have to use disjoint port ranges for individual test, otherwise
parallel test execution leads to unpredictable results.
25 jobs for http_reuseport in 4 minutes and 55 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #313851
amd64 linux docker
archive

00:00:40

passed #313852
amd64 linux docker
build

00:00:50

passed #313853
amd64 linux docker
build-asan

00:00:50

passed #313854
docker
kres-gen

00:00:47

 
  Test
passed #313855
docker delayed
build:darwin

00:00:58

passed #313856
amd64 linux docker
deckard

00:02:30

passed #313857
docker delayed
doc

00:01:00

passed #313858
dind
docker

00:01:48

passed #313859
docker delayed
lint:other

00:00:55

passed #313860
amd64 linux docker delayed
lint:pedantic

00:01:09

passed #313861
amd64 linux docker
lint:scan-build

00:02:32

passed #313862
amd64 linux docker
lint:tidy

00:03:22

canceled #313863
amd64 linux docker
respdiff:basic

00:02:11

passed #313864
amd64 linux docker delayed
test:valgrind

00:01:58

 
  Extended
canceled #313866
respdiff
fwd-tls6-kresd.udp6

canceled #313867
respdiff
fwd-udp6-kresd.udp6

canceled #313871
respdiff
fwd-udp6-unbound.tcp6

canceled #313872
respdiff
fwd-udp6-unbound.tls6

canceled #313870
respdiff
fwd-udp6-unbound.udp6

canceled #313869
respdiff
iter.tls6

canceled #313868
respdiff
iter.udp6

canceled #313865
amd64 linux docker
pytests

canceled #313873
respdiff
resperf:fwd-tls6.udp-asan

canceled #313874
respdiff
resperf:fwd-udp6.udp-asan

canceled #313875
respdiff
resperf:iter.udp-asan