Improve and extend "auto-dnssec" tests

Just testing whether an NSEC3 record exists with the DNSKEY bit set in
its type bitmap is arguably not a solid enough test for how named
processes a signed zone with "auto-dnssec maintain;" set and extra keys
available.  Rather than querying a resolver for a record at the apex of
such a zone, get the whole zone from an authoritative server and run it
through dnssec-verify to improve the comprehensiveness of the test.

Add similar tests for signed zones which have extra keys using a
different algorithm available.

Prevent zone file duplication by making all relevant tests use the same
source file, "auto-nsec.example.db.in".
Status Job ID Name Coverage
  Precheck
passed #231932
amd64 linux
🐞:sid:amd64

00:00:12

passed #231931
amd64 linux
misc:sid:amd64

00:00:17

 
  Build
passed #231943
amd64 linux
asan:sid:amd64

00:03:56

passed #231944
amd64 linux
clang:stretch:amd64

00:02:15

passed #231945
i386 linux
clang:stretch:i386

00:03:13

passed #231933
amd64 linux
docs:sid:amd64

00:00:51

passed #231942
amd64 linux
gcc:bionic:amd64

00:02:59

passed #231934
amd64 linux
gcc:centos6:amd64

00:01:43

passed #231935
amd64 linux
gcc:centos7:amd64

00:01:51

passed #231940
amd64 linux
gcc:fedora29:amd64

00:03:19

passed #231936
amd64 linux
gcc:jessie:amd64

00:01:54

passed #231938
amd64 linux
gcc:sid:amd64

00:02:21

passed #231939
i386 linux
gcc:sid:i386

00:02:17

passed #231937
amd64 linux
gcc:stretch:amd64

00:03:02

passed #231941
amd64 linux
gcc:xenial:amd64

00:02:07

passed #231946
amd64 linux
pkcs11:sid:amd64

00:02:59

 
  Test
passed #231965
amd64 linux
system:asan:sid:amd64

00:07:55

passed #231963
amd64 linux
system:gcc:bionic:amd64

00:06:40

passed #231947
amd64 linux
system:gcc:centos6:amd64

00:06:45

passed #231949
amd64 linux
system:gcc:centos7:amd64

00:06:43

passed #231959
amd64 linux
system:gcc:fedora29:amd64

00:07:01

passed #231970
amd64 linux
system:gcc:jessie:amd64

00:06:22

passed #231971
amd64 linux
system:gcc:sid:amd64

00:06:15

passed #231957
i386 linux
system:gcc:sid:i386

00:06:42

passed #231953
amd64 linux
system:gcc:stretch:amd64

00:06:57

passed #231961
amd64 linux
system:gcc:xenial:amd64

00:06:31

passed #231968
amd64 linux
system:pkcs11:sid:amd64

00:06:59

passed #231966
amd64 linux
unit:asan:sid:amd64

00:00:46

passed #231967
amd64 linux
unit:clang:stretch:amd64

00:00:44

passed #231964
amd64 linux
unit:gcc:bionic:amd64

00:00:50

passed #231948
amd64 linux
unit:gcc:centos6:amd64

00:00:49

passed #231950
amd64 linux
unit:gcc:centos7:amd64

00:00:46

passed #231960
amd64 linux
unit:gcc:fedora29:amd64

00:00:57

passed #231952
amd64 linux
unit:gcc:jessie:amd64

00:00:30

passed #231956
amd64 linux
unit:gcc:sid:amd64

00:00:53

passed #231958
i386 linux
unit:gcc:sid:i386

00:00:53

passed #231954
amd64 linux
unit:gcc:stretch:amd64

00:00:48

passed #231962
amd64 linux
unit:gcc:xenial:amd64

00:00:47

passed #231969
amd64 linux
unit:pkcs11:sid:amd64

00:00:45

failed #231951
amd64 linux
system:gcc:jessie:amd64

00:01:26

failed #231955
amd64 linux
system:gcc:sid:amd64

00:06:54