executing "cudet" without arguments don't show help

[Artem Hrechanychenko]

Detailed bug description:
[root@nailgun ~]# cudet
There are no nodes to check
2016-08-30 13:13:03,477 WARNING (utils) No valid nodes were found which could fit filter parameters.

Steps to reproduce:
1) Deploy any 9.0 cluster
2) configure additional yum repo:http://mirror.fuel-infra.org/mos-repos/centos/mos9.0-centos7/snapshots/proposed-latest/x86_64/
3)yum -y update fuel-nailgun fuel-utils python-fuelclient rubygem-astute
  bash /usr/share/fuel-utils/update-master-node.sh
4) yum install -y python-cudet
5) run cudet

Expected results:
usage: cudet [-h] [-f] [-c CONFIG] [-e [ENV [ENV ...]]] [-n [NODE [NODE ...]]]
             [-d]

optional arguments:
  -h, --help show this help message and exit
  -f, --fake Do not perform remote commands, use already collected
                        data
  -c CONFIG, --config CONFIG
                        Path to user config file
  -e [ENV [ENV ...]], --env [ENV [ENV ...]]
                        Perform check only for specified environment ids
  -n [NODE [NODE ...]], --node [NODE [NODE ...]]
                        Perform check only for specified node ids
  -d, --debug Turn on debug messages
Actual result:
 There are no nodes to check
2016-08-30 13:13:03,477 WARNING (utils) No valid nodes were found which could fit filter parameters.

[Anton Samoylov (asamoylov)]

This is an expected behavior. Cudet doesn't show help message if you run it w/o arguments.
Arguments '-e/--env' and '-n/--node' are optional and if they aren't provided, cudet will check all nodes listed by nailgun service.
Help message for cudet tool is available via '-h/--help' optional argument.