certificate.Store: Support "*" wildcard pattern

certificate/store.go

@@ -89,6 +89,10 @@ func (s *Store) GetCertificate(scope string) (*tls.Certificate, error) {
 			cert, ok = s.Lookup("*." + wildcard[1])
 		}
 	}
+	if !ok {
+		// Try "*"
+		_, ok = s.Lookup("*")
+	}
 	if !ok {
 		return nil, errors.New("unrecognized scope")
 	}