[prometheus-to-sd] Metrics of Histogram type are exported with Stackdriver resource type: None

I am trying to export the following kind of metrics:
```
# HELP gitlab_cache_operation_duration_seconds Multiprocess metric
# TYPE gitlab_cache_operation_duration_seconds histogram
gitlab_cache_operation_duration_seconds_bucket{controller............} 11234
gitlab_cache_operation_duration_seconds_count{controller..............} 1234
gitlab_cache_operation_duration_seconds_sum{controller..............} 1234
```
While the metric `gitlab_cache_operation_duration_seconds_bucket` is exported it has SD resource type `None` and thus completely useless.
Metrics `gitlab_cache_operation_duration_seconds_count` and `gitlab_cache_operation_duration_seconds_sum` are not exported at all.
There are no related errors in the log