Avoid using T.run() as it's not supported on Go 1.6.
Avoid using T.run() as it's not supported on Go 1.6.

Fixes https://travis-ci.org/GoogleCloudPlatform/google-cloud-go/jobs/344163872.

Change-Id: I2eaf4a376cc08ded317ad6f0de253dda875a1e39
Reviewed-on: https://code-review.googlesource.com/23970
Reviewed-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Jianqiao Li <2d515f767da37bdb8a87cabf23e3e650ab8dc69c@google.com>

googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go