The merge-new-params-nic-config-script.py previosly had the
'Controller' role as the default for --role-name. It is not
obvious that this parameter must be changed when merging
nic config templates.
Remove the default and make the argument required. Improves
UX since user error is less likely.
Making the mistake of using a Role with too many networks
is'nt as forgiving since we now only pass parameters for
the role.networks.
Related-Bug: #1800811
Change-Id: Iff9e364db66ad09a30ac10a7814a3c01d50caf58