Should 'topics.testIamPermissions' be wrapped as 'check_iam_permissions'?

[tseaver]

See: #1642 (comment) and ff.

Likewise subscriptions.testIamPermission.

@jgeewax if you decide so, please assign the issue to me; otherwise, just close it.

[jgeewax]

I'm a fan of check unless we have an awesome reason not to...