Avoid cloning the message envelope when iterating

In iterate mediator json message flow, we don't need to clone the entire envelope since we are replacing it with iterated message later.
Adding an empty envelope instead improves the performance.
Fixes wso2/api-manager/issues/2196

modules/core/src/main/java/org/apache/synapse/mediators/eip/splitter/IterateMediator.java

@@ -23,9 +23,12 @@
 import com.google.gson.JsonElement;
 import com.google.gson.JsonParser;
 import com.jayway.jsonpath.JsonPath;
+import org.apache.axiom.om.OMAbstractFactory;
 import org.apache.axiom.om.OMElement;
 import org.apache.axiom.om.OMNode;
+import org.apache.axiom.soap.SOAP11Constants;
 import org.apache.axiom.soap.SOAPEnvelope;
+import org.apache.axiom.soap.SOAPFactory;
 import org.apache.axis2.AxisFault;
 import org.apache.axis2.Constants;
 import org.apache.axis2.context.OperationContext;
@@ -372,10 +375,17 @@ private MessageContext getIteratedMessage(MessageContext synCtx, int msgNumber,
             throws AxisFault, JaxenException {
 
         // clone the message for the mediation in iteration
-        MessageContext newCtx = MessageHelper.cloneMessageContext(synCtx);
-
-        //Remove the original jsonstream from the context
-        JsonUtil.removeJsonPayload(((Axis2MessageContext) newCtx).getAxis2MessageContext());
+        MessageContext newCtx = MessageHelper.cloneMessageContext(synCtx, false, false);
+        // Adding an empty envelope since JsonUtil.getNewJsonPayload requires an envelope
+        SOAPFactory fac;
+        if (SOAP11Constants.SOAP_ENVELOPE_NAMESPACE_URI
+                .equals(synCtx.getEnvelope().getBody().getNamespace().getNamespaceURI())) {
+            fac = OMAbstractFactory.getSOAP11Factory();
+        } else {
+            fac = OMAbstractFactory.getSOAP12Factory();
+        }
+        SOAPEnvelope newEnvelope = fac.getDefaultEnvelope();
+        newCtx.setEnvelope(newEnvelope);
 
         if (id != null) {
             // set the parent correlation details to the cloned MC -