Spec qualified names (label keys) more tightly

It can be a (DNS_SUBDOMAIN/)?label, but we were validating it
incorrectly before.

pkg/util/validation_test.go

@@ -168,24 +168,30 @@ func TestIsQualifiedName(t *testing.T) {
 		"1-num.2-num/3-num",
 		"1234/5678",
 		"1.2.3.4/5678",
-		"UppercaseIsOK123",
+		"Uppercase_Is_OK_123",
+		"example.com/Uppercase_Is_OK_123",
+		strings.Repeat("a", 63),
+		strings.Repeat("a", 253) + "/" + strings.Repeat("b", 63),
 	}
 	for i := range successCases {
 		if !IsQualifiedName(successCases[i]) {
-			t.Errorf("case[%d] expected success", i)
+			t.Errorf("case[%d]: %q: expected success", i, successCases[i])
 		}
 	}
 
 	errorCases := []string{
 		"nospecialchars%^=@",
 		"cantendwithadash-",
+		"-cantstartwithadash-",
 		"only/one/slash",
-		strings.Repeat("a", 254),
-		"-cantstartwithadash",
+		"Example.com/abc",
+		"example_com/abc",
+		strings.Repeat("a", 64),
+		strings.Repeat("a", 254) + "/abc",
 	}
 	for i := range errorCases {
 		if IsQualifiedName(errorCases[i]) {
-			t.Errorf("case[%d] expected failure", i)
+			t.Errorf("case[%d]: %q: expected failure", i, errorCases[i])
 		}
 	}
 }