Comment 0 for bug 1670123

There are two "completion" in the subcommand table: bash-completion and bash_completion. They are following:
'bash_completion': MagnumClientArgumentParser(prog='magnum bash_completion', usage=None, description=None, version=None, formatter_class=<class 'magnumclient.shell.OpenStackHelpFormatter'>, conflict_handler='error', add_help=False)
'bash-completion': MagnumClientArgumentParser(prog='magnum bash-completion', usage=None, description="Prints arguments for bash-completion.\n\n Prints all of the commands and options to stdout so that the\n magnum.bash_completion script doesn't have to hard code them.\n ", version=None, formatter_class=<class 'magnumclient.shell.OpenStackHelpFormatter'>, conflict_handler='error', add_help=False)

But the command is "magnum bash-completion", so remove "bash_completion".