s3:utils/net: Add new option 'unregister' in 'net ads dns' command.
This new option allows DNS names to be unregistered and removes all
IP entries for a given name in the specified AD server.
Signed-off-by: Shyamsunder Rathi <shyam.rathi@nutanic.com> Reviewed-by: Richard SHarpe <rsharpe@samba.org> Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Richard Sharpe <sharpe@samba.org>
Autobuild-Date(master): Mon Jun 27 20:43:26 CEST 2016 on sn-devel-144