cmds.xxx .CmdXxx._run(): Add print_help()

All commands that do load_subcommands() should have a default _run() implementation which calls print_help(), add them.
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/cmds/CmdPosix.py

@@ -20,5 +20,12 @@ class CmdPosix(Cmd):  # export
         )
         self.load_subcommands()
 
+    async def _run(self, args):
+        import sys
+
+        # Missing subcommand
+        self.parser.print_help()
+        sys.exit(1)
+
     def add_arguments(self, parser: ArgumentParser) -> None:
         super().add_arguments(parser)