Increase timeout in the rndc deadlock test

The timeout originally picked for "rndc status" invocations (2 seconds)
in the test attempting to reproduce a deadlock caused by running
multiple "rndc addzone", "rndc modzone", and "rndc delzone" commands
concurrently causes intermittent failures of the "addzone" system test
in GitLab CI.  Increase the timeout to 10 seconds to make such failures
less probable.  Adjust code comments accordingly.
70 jobs for !5163 with 2763-increase-timeout-in-the-rndc-deadlock-test in 3 minutes and 27 seconds (queued for 11 seconds)
latest detached
Status Job ID Name Coverage
  Autoconf
passed #1805774
amd64 linux
autoreconf

00:00:18

 
  Precheck
passed #1805776
amd64 linux
clang-format

00:00:17

canceled #1805777
amd64 linux
coccinelle

00:03:22

passed #1805778
amd64 linux
danger

00:00:18

passed #1805775
amd64 linux
misc

00:00:19

passed #1805779
amd64 linux
tarball-create

00:02:18

 
  Build
passed #1805792
amd64 linux
clang:asan

00:02:04

passed #1805795
amd64 linux
clang:buster:amd64

00:01:11

passed #1805798
amd64 libvirt
clang:freebsd12:amd64

00:01:05

canceled #1805799
amd64 libvirt
clang:freebsd13:amd64

00:02:53

passed #1805800
amd64 libvirt
clang:openbsd:amd64

00:02:30

passed #1805794
amd64 linux
clang:tsan

00:01:19

passed #1805780
amd64 linux
gcc:alpine3.13:amd64

00:00:59

passed #1805791
amd64 linux
gcc:asan

00:02:07

passed #1805789
amd64 linux
gcc:bionic:amd64

00:00:59

passed #1805784
amd64 linux
gcc:buster:amd64

00:00:53

passed #1805781
amd64 linux
gcc:centos7:amd64

00:00:52

passed #1805782
amd64 linux
gcc:centos8:amd64

00:00:59

passed #1805790
amd64 linux
gcc:focal:amd64

00:00:58

passed #1805786
amd64 linux
gcc:out-of-tree

00:01:02

passed #1805785
amd64 linux
gcc:sid:amd64

00:01:11

passed #1805796
amd64 linux
gcc:softhsm2.4

00:00:54

passed #1805797
amd64 linux
gcc:softhsm2.6

00:01:00

passed #1805783
amd64 linux
gcc:stretch:amd64

00:01:26

canceled #1805787
amd64 linux
gcc:tarball

00:00:38

passed #1805793
amd64 linux
gcc:tsan

00:01:13

passed #1805788
amd64 linux
gcc:tumbleweed:amd64

00:00:58

 
  Unit
canceled #1805811
amd64 linux
unit:clang:asan

00:00:26

canceled #1805814
amd64 linux
unit:clang:buster:amd64

00:01:08

canceled #1805817
amd64 libvirt
unit:clang:freebsd12:amd64

00:01:31

canceled #1805818
amd64 libvirt
unit:clang:freebsd13:amd64

canceled #1805819
amd64 libvirt
unit:clang:openbsd:amd64

00:00:11

canceled #1805813
amd64 linux
unit:clang:tsan

00:00:58

passed #1805801
amd64 linux
unit:gcc:alpine3.13:amd64

00:01:41

canceled #1805810
amd64 linux
unit:gcc:asan

00:00:32

canceled #1805808
amd64 linux
unit:gcc:bionic:amd64

00:01:29

canceled #1805805
amd64 linux
unit:gcc:buster:amd64

00:01:45

passed #1805802
amd64 linux
unit:gcc:centos7:amd64

00:01:35

passed #1805803
amd64 linux
unit:gcc:centos8:amd64

00:01:34

canceled #1805809
amd64 linux
unit:gcc:focal:amd64

00:01:28

canceled #1805806
amd64 linux
unit:gcc:sid:amd64

00:01:31

passed #1805815
amd64 linux
unit:gcc:softhsm2.4

00:01:31

passed #1805816
amd64 linux
unit:gcc:softhsm2.6

00:01:31

passed #1805804
amd64 linux
unit:gcc:stretch:amd64

00:00:28

canceled #1805812
amd64 linux
unit:gcc:tsan

00:00:59

passed #1805807
amd64 linux
unit:gcc:tumbleweed:amd64

00:01:35

 
  System
canceled #1805830
amd64 linux
system:clang:asan

00:00:13

canceled #1805833
amd64 linux
system:clang:buster:amd64

00:00:11

canceled #1805836
amd64 libvirt
system:clang:freebsd12:amd64

00:01:31

canceled #1805837
amd64 libvirt
system:clang:freebsd13:amd64

canceled #1805832
amd64 linux
system:clang:tsan

00:00:13

canceled #1805820
amd64 linux
system:gcc:alpine3.13:amd64

00:01:42

canceled #1805829
amd64 linux
system:gcc:asan

00:00:16

canceled #1805827
amd64 linux
system:gcc:bionic:amd64

00:01:22

canceled #1805824
amd64 linux
system:gcc:buster:amd64

canceled #1805821
amd64 linux
system:gcc:centos7:amd64

00:01:40

canceled #1805822
amd64 linux
system:gcc:centos8:amd64

00:01:39

canceled #1805828
amd64 linux
system:gcc:focal:amd64

00:01:20

canceled #1805825
amd64 linux
system:gcc:sid:amd64

00:01:29

canceled #1805834
amd64 linux
system:gcc:softhsm2.4

00:01:59

canceled #1805835
amd64 linux
system:gcc:softhsm2.6

00:01:44

canceled #1805823
amd64 linux
system:gcc:stretch:amd64

00:00:38

canceled #1805831
amd64 linux
system:gcc:tsan

00:00:38

canceled #1805826
amd64 linux
system:gcc:tumbleweed:amd64

00:01:39

 
  Docs
passed #1805838
amd64 linux
docs

00:01:11

 
  Postcheck
passed #1805842
amd64 linux
cppcheck

00:00:30

passed #1805839
amd64 linux
flake8

00:00:21

canceled #1805843
amd64 linux
gcov

passed #1805840
amd64 linux
pylint

00:00:42

canceled #1805841
amd64 linux
scan-build

00:02:43