add unit tests for defaults to feature gelf
add unit tests for defaults to feature gelf

Icinga/puppet-icinga2,Icinga/puppet-icinga2-rewrite,Icinga/puppet-icinga2,lazyfrosch/puppet-icinga2,lazyfrosch/puppet-icinga2,Icinga/puppet-icinga2-rewrite,lazyfrosch/puppet-icinga2,Icinga/puppet-icinga2-rewrite