samba-tool: error handling improvements in delegation.py and samdb.py

[Andrew Tridgell]

Hi Giampaolo,

I had a look at these patches today. Two small comments:

 - the patches add an optional flags_str argument to
   toggle_userAccountFlags(), defaulting to None. If it defaults to
   None, then you shouldn't use it in a print statement without checking
   if it is None. Maybe make it non-optional and update the only other
   user of the function in samdb.py?

 - as we discussed earlier today, the patch to
   cmd_domain_machinepassword() looks a bit strange we we are using a
   variable 'secret' to represent an account name. I think we just need
   to change the takes_args to be ["accountname"] and use 'accountname'
   instead of 'secret' for the variable. Can you check that is right,
   test and fix?

Cheers, Tridge