python/samba: add on optional 'special_name' argument to CredentialsOptions()

python/samba: add on optional 'special_name' argument to CredentialsOptions()

This way we have have two sets or credentials on the command line,
while at least one uses some prefix (special_name) for the arguments.

The default options without special_name are:

  Credentials Options:
    --simple-bind-dn=DN
                        DN to use for a simple bind
    --password=PASSWORD
                        Password
    -U USERNAME, --username=USERNAME
                        Username
    -W WORKGROUP, --workgroup=WORKGROUP
                        Workgroup
    -N, --no-pass       Don't ask for a password
    -k KERBEROS, --kerberos=KERBEROS
                        Use Kerberos
    --ipaddress=IPADDRESS
                        IP address of server
    -P, --machine-pass  Use stored machine account password

With special_name='local-dc' it's:

  Credentials Options (local-dc):
    --local-dc-simple-bind-dn=DN
                        DN to use for a simple bind
    --local-dc-password=PASSWORD
                        Password
    --local-dc-username=USERNAME
                        Username
    --local-dc-workgroup=WORKGROUP
                        Workgroup
    --local-dc-no-pass  Don't ask for a password
    --local-dc-kerberos=KERBEROS
                        Use Kerberos
    --local-dc-ipaddress=IPADDRESS
                        IP address of server
    --local-dc-machine-pass
                        Use stored machine account password

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>