net: Use samba default command line arguments.

net: Use samba default command line arguments.

Attention:

The meaning of the -N flag changed.
To get the old meaning for net groupmap set, use the long option --ntname
The long option for using kerberos changed from --kerberos to --use-kerberos

net rpc commands will now prompt for a password if none is given.

As a benefit, net will now accept an authentication file like other samba
command line tools. So no need to specify the password on the command line in
scripts anymore.

This should fix bug #6357

Signed-off-by: Kai Blin <kai@samba.org>