cmd/go: add another test case for package/module ambiguity in 'go get'
For #37438
Change-Id: Iae00ef7f97144e85f4f710cdb3087c2548b4b8f0
Reviewed-on: https://go-review.googlesource.com/c/go/+/256799
Trust: Bryan C. Mills <bcmills@google.com>
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Michael Matloob <matloob@golang.org> Reviewed-by: Jay Conrod <jayconrod@google.com>