Remove group resource

Dont check for running group resources.
```ruby
pacemaker_group "g-glance" do
  action [:stop, :delete]
  only_if "crm configure show g-glance"
end 
```
when `only_if` is evaluated, `Mixlib::ShellOut::ShellCommandFailedexception` is raised and the recipe exits fatally.

in the [`running?`](https://github.com/crowbar/barclamp-pacemaker/blob/release/roxy/master/chef/cookbooks/pacemaker/libraries/pacemaker/resource.rb#L14) method following cmd is evaluated:
`crm resource status g-glance` which returns 1 and causes the Exception.

`crm resource status` contains groups, but not i.e. `g-glance`, the `g-$barclamp` ones which is questionable.