Fix validation bug in fake OCPP 2.1 CSMS

The fake OCPP 2.1 CSMS checkConfirmation() implementation missed calling
the super method for older protocol versions, causing the check to be
omitted for these. Add the missing super call.

Author: robert-s-ubi

ocpp-v2-test/src/main/java/eu/chargetime/ocpp/test/OCPP21MultiProtocolFakeCSMS.java

@@ -89,12 +89,16 @@ public void sendGetVariablesRequest() {
 
   @Override
   void checkConfirmation(Confirmation confirmation) {
-    if (confirmation instanceof GetVariablesResponse) {
-      GetVariablesResponse getVariablesResponse = (GetVariablesResponse) confirmation;
-      if (getVariablesResponse.getGetVariableResult().length != 1) {
-        throw new PropertyConstraintException(
-            getVariablesResponse.getGetVariableResult().length,
-            "GetVariablesResponse getVariableResult length must be 1");
+    if (!OCPP2_1.equals(getDummyHandlers().getCurrentProtocolVersion())) {
+      super.checkConfirmation(confirmation);
+    } else {
+      if (confirmation instanceof GetVariablesResponse) {
+        GetVariablesResponse getVariablesResponse = (GetVariablesResponse) confirmation;
+        if (getVariablesResponse.getGetVariableResult().length != 1) {
+          throw new PropertyConstraintException(
+              getVariablesResponse.getGetVariableResult().length,
+              "GetVariablesResponse getVariableResult length must be 1");
+        }
       }
     }
   }