kas: Simplify setup of plugin argument parsers

By defining the plugin name and help message as attributes of the plugin
class we can move the argument parser creation up into the
kas_get_argparser() function. This will allow us to further reduce
duplication in following commits.

Signed-off-by: Paul Barker <pbarker@konsulko.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/kas.py

@@ -121,7 +121,8 @@ def kas_get_argparser():
         ext_plugin.load()
 
     for plugin in getattr(kasplugin, 'plugins', []):
-        plugin.get_argparser(subparser)
+        plugin_parser = subparser.add_parser(plugin.name, help=plugin.helpmsg)
+        plugin.setup_parser(plugin_parser)
 
     return parser