tests: dnsserver: Add a update test with name set to '.'

tests: dnsserver: Add a update test with name set to '.'

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Tue Jul 29 19:33:19 CEST 2014 on sn-devel-104

(cherry picked from commit 6d104182d9667e4f996439d24cfa052f34098ce4)

Bug: https://bugzilla.samba.org/show_bug.cgi?id=10742
samba-tool dns add 172.31.9.161 s4xdom.base . NS mydns.org. => NO_MEMORY

Autobuild-User(v4-0-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-0-test): Thu Aug 21 18:59:16 CEST 2014 on sn-devel-104