cmd/guru: fix tests now that go1.9 go/types returns fake packages

The go1.9 type checker now returns fake packages in addition to an
error if the package was not found at all.  This changes the behavior
of guru in a release-specific way, requiring the test to be split into
a common part and a go1.9-specific part.

In hindsight, perhaps it would have been better to place the
expectation in a comment alongside the query so that they can be
easily enabled or disabled together.  (The downside of that design is
that you can't batch-update all the expectations to match the actual
behavior.)

Change-Id: I58054adec428fbab7fe3c57097aefc827f89a46e
Reviewed-on: https://go-review.googlesource.com/37865
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
10 files changed