Code style: correct uses of 'fail' and 'raise'
Code style: correct uses of 'fail' and 'raise'

Fix the code style error "Style/SignalException" found by
latest RuboCop, see:

http://www.rubydoc.info/gems/rubocop/RuboCop/Cop/Style/SignalException

Code style error was:

recipes/commons_os.rb:33:5: C: Style/SignalException: Always use raise to signal exceptions.
    fail "`#{node['platform']}` is not supported!"
    ^^^^
recipes/commons_os.rb:36:3: C: Style/SignalException: Always use raise to signal exceptions.
  fail "`#{node['platform']}` is not supported!"
  ^^^^

Signed-off-by: Stephan Linz <0c883f969082385953c36ae90fd905b7f154694b@li-pro.net>

lipro-cookbooks/test-helper,rexut/lpn-cookbooks-test-helper,lipro-cookbooks/test-helper,rexut/lpn-cookbooks-test-helper