pytest/test_tcp_pipelining: longer delay for first query

In our CI, this test ocassionally fails. This is most likely due to
delays in kernel processing due to many virtualization layers coupled
with massive paralelization of tests.

Closes #427
31 jobs for <span class="ref-name">ci-stabilize-pytests</span> in 9 minutes and 32 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #217345
docker linux amd64
build:asan:linux:amd64

00:01:14

passed #217344
docker linux amd64
build:linux:amd64

00:01:14

passed #217346
docker linux amd64 allowed to fail
srpm

00:00:44

 
  Test
passed #217355
docker linux amd64
deckard:linux:amd64

00:01:45

passed #217363
privileged
distro:epel-7

00:01:58

passed #217362
privileged
distro:fedora-29

00:02:28

passed #217354
docker
doc

00:00:50

passed #217352
dind
docker:build

00:01:52

passed #217353
docker linux amd64
installcheck:linux:amd64

00:00:56

passed #217356
docker linux amd64
installcheck:valgrind:linux:amd64

00:01:44

passed #217349
docker
lint:c

00:02:11

passed #217350
docker
lint:clang-scan-build

00:01:00

passed #217348
docker
lint:lua

00:00:39

passed #217347
docker linux amd64
lint:pedantic

00:01:18

passed #217357
docker
osx:build

00:02:41

passed #217359
docker linux amd64
pytests:lint

00:00:28

passed #217360
docker linux amd64
pytests:run

00:02:18

passed #217361
docker linux amd64
respdiff:iter:udp:linux:amd64

00:04:45

passed #217351
docker linux amd64
test:linux:amd64

00:00:58

passed #217358
docker linux amd64
test:linux:amd64:valgrind

00:01:09

 
  Extended
passed #217364
docker linux amd64
pytests:extended

00:03:28

passed #217365
respdiff
respdiff:fwd-tls6-kresd.udp6

00:00:17

passed #217366
respdiff
respdiff:fwd-udp6-kresd.udp6

00:00:19

passed #217370
respdiff
respdiff:fwd-udp6-unbound.tcp6

00:00:20

passed #217371
respdiff
respdiff:fwd-udp6-unbound.tls6

00:00:19

passed #217369
respdiff
respdiff:fwd-udp6-unbound.udp6

00:00:19

passed #217368
respdiff
respdiff:iter.tls6

00:00:19

passed #217367
respdiff
respdiff:iter.udp6

00:00:19

passed #217372
respdiff
resperf:fwd-tls6.udp-asan

00:00:19

passed #217373
respdiff
resperf:fwd-udp6.udp-asan

00:00:19

passed #217374
respdiff
resperf:iter.udp-asan

00:00:19