Some users would want to use Consul namespaces when using the Consul
backend but the version of the Consul API client we use is too old and
don't support them. In preparation for this change this patch just update
it the client and replace testutil.NewTestServerConfig() by
testutil.NewTestServerConfigT() in the tests.
This is part of a general effort to move all of Terraform's non-library
package surface under internal in order to reinforce that these are for
internal use within Terraform only.
If you were previously importing packages under this prefix into an
external codebase, you could pin to an earlier release tag as an interim
solution until you've make a plan to achieve the same functionality some
other way.