LU-8621 utils: cmd help to stdout or short cmd error

- Changed to print command help to stdout
- Changed to output short error message for an unrecognized command

Test-Parameters: trivial
Signed-off-by: Aleksei Alyaev <aalyaev@ddn.com>
Change-Id: I67616ddb576e3347a2da130b3a731a6bf8730185
Reviewed-on: https://review.whamcloud.com/47162
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>