crypto/internal/fips140test: add a test for a non-approved function

crypto/internal/fips140test: add a test for a non-approved function

Change-Id: I6a6a46560bfca588e5874f3769f33b561c33096a
Reviewed-on: https://go-review.googlesource.com/c/go/+/652415
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>