Submitting empty attributes

[WhatsARanjit]

Previous issues:

• https://github.com/puppetlabs/prosvcs-node_manager/issues/48
• https://github.com/puppetlabs/prosvcs-node_manager/issues/36

If you're trying to remove all classification or remove all rules, you might try:

node_group { 'test':
  rule    => [],
  classes => {},
}

...but this translates to undef and so it's an unmanaged attribute. Need a feature to be able to submit an empty value to clear out what is there.

[WhatsARanjit]

Fixed in #14.