Fix tip-level rake test tasks (#2442)
Fix tip-level rake test tasks (#2442)

When changing to sub-directory, we want to shell out to the rake task.
These tasks were changed erroneously, so change them back.
dazuma/google-cloud-ruby,dazuma/google-cloud-ruby,dazuma/google-cloud-ruby,quartzmo/google-cloud-ruby,dazuma/google-cloud-ruby,dazuma/google-cloud-ruby,googleapis/google-cloud-ruby,quartzmo/google-cloud-ruby,googleapis/google-cloud-ruby,quartzmo/gcloud-ruby,quartzmo/google-cloud-ruby,googleapis/google-cloud-ruby,quartzmo/google-cloud-ruby,blowmage/gcloud-ruby,quartzmo/google-cloud-ruby,googleapis/google-cloud-ruby,googleapis/google-cloud-ruby,quartzmo/google-cloud-ruby,dazuma/google-cloud-ruby,googleapis/google-cloud-ruby