samba-tool: improve computer management commands

samba-tool: improve computer management commands

This pathch is based on Björn Baumbach's work:
1. Add `--ip-address` option for create subcommand, to allow user set DNS
A or AAAA records while creating the computer.
2. Delete above DNS records while deleting the computer.
3. Add `--service-principal-name` option for create command, to allow user
set `servicePrincipalName` while creating the computer.
4. Tests.

Signed-off-by: Joe Guo <joeg@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>