Ruler does not expose shipper metrics

[OGKevin]

Thanos, Prometheus and Golang version used:

0.10.1

Object Storage Provider:
GCS

What happened:
Ruler failed to upload to GCS bucket, by reading the code, it should increase and expose the following metric:

thanos/pkg/shipper/shipper.go

Lines 338 to 340 in 4a23b36

	if uploadErrs > 0 {
	s.metrics.uploadFailures.Add(float64(uploadErrs))
	return uploaded, errors.Errorf("failed to sync %v blocks", uploadErrs)

However, this does not happen due to missing prom register:

thanos/cmd/thanos/rule.go

Line 632 in 4a23b36

s := shipper.New(logger, nil, dataDir, bkt, func() labels.Labels { return lset }, metadata.RulerSource)

What you expected to happen:
Ruler to expose this metric.

How to reproduce it (as minimally and precisely as possible):

1. run ruler with bad bucket config
2. let the upload fail
3. check if metric is exposed, this should not be the case

Full logs to relevant components:

Anything else we need to know: