Align default transaction name to '<method> unknown route' (#542)

Author: felixbarny

apm-agent-plugins/apm-servlet-plugin/src/main/java/co/elastic/apm/agent/servlet/ServletTransactionHelper.java

@@ -167,7 +167,7 @@ void applyDefaultTransactionName(String method, String servletPath, @Nullable St
                 }
             }
         } else {
-            transactionName.append(method);
+            transactionName.append(method).append(" unknown route");
         }
     }