Generates tag for a single host test failing locally

Test fails with:

```ruby
Error:
TagsGeneratorTest#test_0001_generates tags for a single host:
NoMethodError: undefined method `first' for nil:NilClass
    /home/vagrant/foreman_rh_cloud/test/unit/tags_generator_test.rb:66:in `block in <class:TagsGeneratorTest>'
```