Move version out of SDK. For now it's a copy rather than move: the part not addressed by this change is sdk/helper/useragent.String, which we'll want to remove in favour of PluginString. That will have to wait until we've removed uses of useragent.String from all builtins.
Some commands didn't setup a local test server since they didn't need
it. Other commands didn't setup a local test server because Seth forgot.
Long story short, I kept seeing weird requests to my Vault server when I
ran tests, and that should never happen. This ensures all test requests
will go to a test Vault instance.
Benchmarks show this adds 0.4s to the command test suite.
