allow empty permission fields

fixes https://github.com/puppetlabs/puppetlabs-rabbitmq/issues/172
add tests for empty permission fields
Remove problematic package dependency

This dependency is already defined in the rabbitmq::repo::rhel class
and fails altogether when $manage_repos is set to false. I don't
understand why the tests don't catch that though.
Merge pull request #191 from ckaenzig/fix-package-dependency

Remove problematic package dependency
Merge pull request #183 from DECK36/pull-req-permissions

allow empty permission fields