kola: really make requiredTag required

Before, even though a test had a required tag, explicitly passing a
pattern which matched that test name would still include it. I thought
that would be convenient, but it makes the logic less predictable. Since
we don't use many required tags today, let's instead opt for being more
explicit and always actually require the tag.

Motivated by coreos/rpm-ostree#4806 (comment).

mantle/kola/harness.go

@@ -539,8 +539,10 @@ func filterTests(tests map[string]*register.Test, patterns []string, pltfrm stri
 		}
 
 		if t.RequiredTag != "" && // if the test has a required tag...
-			!HasString(t.RequiredTag, positiveTags) && // and that tag was not provided by the user...
-			(!userTypedPattern || !nameMatch) { // and the user didn't request it by name...
+			!HasString(t.RequiredTag, positiveTags) { // and that tag was not provided by the user
+			if userTypedPattern && nameMatch {
+				fmt.Printf("⏭️  Skipping kola test \"%s\" with required tag \"%s\"\n", t.Name, t.RequiredTag)
+			}
 			continue // then skip it
 		}