libnet_join: add SPNs for additional-dns-hostnames entries

and set msDS-AdditionalDnsHostName to the specified list.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14116

Signed-off-by: Isaac Boukris <iboukris@redhat.com>
Reviewed-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Alexander Bokovoy <ab@samba.org>

Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Fri Oct 25 10:43:08 UTC 2019 on sn-devel-184
31 jobs for iboukris-v4-11-test in 62 minutes and 39 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Build
passed centos7-samba-o3 #334827996
docker shared

00:35:12

passed ctdb #334827974
docker shared

00:35:44

passed debian9-samba-o3 #334827992
docker shared

00:33:55

passed fedora29-samba-o3 #334827997
docker shared

00:33:43

passed fedora30-samba-o3 #334827998
docker shared

00:34:49

passed opensuse150-samba-o3 #334827994
docker shared

00:41:11

passed opensuse151-samba-o3 #334827995
docker shared

00:37:30

passed others #334827959
docker shared

00:14:12

passed samba #334827960
docker shared

00:24:28

passed samba-ad-dc-1 #334827980
docker samba-ci-private

00:36:16

passed samba-ad-dc-2 #334827967
docker shared

00:58:22

passed samba-ad-dc-3 #334827968
docker shared

00:45:29

passed samba-ad-dc-4 #334827969
docker shared

01:02:34

passed samba-ad-dc-5 #334827970
docker shared

00:46:19

passed samba-ad-dc-6 #334827971
docker shared

00:32:59

passed samba-ad-dc-backup #334827977
docker samba-ci-private

00:39:16

passed samba-ad-dc-ntvfs #334827976
docker shared

00:45:40

passed samba-ad-member #334827966
docker shared

00:20:13

passed samba-ctdb #334827975
docker shared

00:21:57

passed samba-fileserver #334827978
docker samba-ci-private

00:26:52

passed samba-libs #334827972
docker shared

00:37:46

passed samba-none-env #334827961
docker shared

01:01:10

passed samba-nopython #334827962
docker shared

00:32:48

passed samba-nopython-py2 #334827963
docker shared

00:43:39

passed samba-nt4 #334827983
docker samba-ci-private

00:46:09

passed samba-schemaupgrade #334827984
docker samba-ci-private

00:24:49

passed samba-static #334827973
docker shared

01:01:09

passed samba-systemkrb5 #334827964
docker shared

00:20:16

passed samba-xc #334827965
docker shared

00:06:38

passed ubuntu1604-samba-o3 #334827989
docker shared

00:34:15

passed ubuntu1804-samba-o3 #334827985
docker shared

00:35:44