samba-tool: Fixed bugs to determine min and max # of allowed arguments

samba-tool: Fixed bugs to determine min and max # of allowed arguments

Fixed the bugs in the code to determine both the min and the max # of allowed arguments
Changed the argument suffix convention from "*" to "+" to represent one or more arguments as:
 1. It follows the Regular expression convention ("*" means 0 or more)
 2. It is what was missing in terms of functionality
NB Currently, no command is using the "*/+", but it is a good thing to have to help out the validation of the args if/when in the future
we have such need

Signed-off-by: Andrew Tridgell <tridge@samba.org>