Use docker/distribution/reference.ParseNormalizedNamed

docker/distribution/reference.ParseNamed now (as of
6170ac53daed40ebbebc9fe5f482495d01f09f12) refuses input in a
non-fully-explicit form; the new ParseNormalizedNamed accepts it and
normalizes it into the fully explicit form.  (One would expect it to be
the other way around…)

So, use ParseNormalizedNamed now.  This is a minimal fix for the failing
tests.

Because docker/distribution/reference now does all the normalization, we
can use it and drop our docker/docker/reference fork (which will go away
upstream), at least in the short term.  (Longer-term we may need to
reintroduce it again if projectatomic/docker decided to modify _that_.)
But that’s more than just fixing the tests, so that will be a separate
PR.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

docker/reference/reference.go

@@ -56,7 +56,7 @@ type Canonical interface {
 // returned.
 // If an error was encountered it is returned, along with a nil Reference.
 func ParseNamed(s string) (Named, error) {
-	named, err := distreference.ParseNamed(s)
+	named, err := distreference.ParseNormalizedNamed(s)
 	if err != nil {
 		return nil, errors.Wrapf(err, "Error parsing reference: %q is not a valid repository/tag", s)
 	}