In these cases, continuing after a non nil error will result in a nil
dereference in panic.
Change the `assert.Check` to `assert.NilError` to avoid that.
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
This allows stubbing the provider for a test without side effects for
other tests, making it no longer needed to reset it to its original
value in a defer()
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
