test_cli: Fix test_run_help and test_list_help
Due to an incomplete command passed to the HelpFormatter.format
method,
the text alignment in the usage_prefix
variable was not the same as the
command output generated by click.
Those tests started to fail since the recent growth of available loaders as click wraps help lines to 80 columns.
Migrated from D5214 (view on Phabricator)