title: $batch request resulting in error "Default changeset implementation allows only one operation"
body: <p>I am making a worklist application using SAPUI5. The problem is that when I create an entry and then create another one right after that, I get the following error:</p>
  <blockquote>
  <p>Default changeset implementation allows only one operation.</p>
  </blockquote>
  <p>I checked the <code>$batch</code> header and I see that there is a MERGE and a POST, with the MERGE updating the previous entry for some reason. Can anyone shed some light? Could it be a backend error and not a UI5 error?</p>
  <p>Creating the new entry:</p>
  <pre class="lang-js prettyprint-override"><code>_onMetadataLoaded: function() {
    var oModel = this.getView().getModel();
    var that = this;
    // ...
    oModel.read(&quot;/USERS_SET&quot;, {
      success: function(oData) {
        var oProperties = {
          Qmnum: &quot;0&quot;,
          Otherstuff: &quot;cool&quot;
        };
        that._oContext = that._oView.getModel().createEntry(&quot;/ENTITYSET&quot;, {
          properties: oProperties
        });
        that.getView().setBindingContext(that._oContext);
        // ...
      }
    });
  },
  
  handleSavePress: function(oEvent) {
    // ...
    this.getView().getModel().submitChanges({
      success: function(oData) {
        // ...
      },
      error: function(oError) {
        // ...
      }
    });
  },
  </code></pre>