Es reader update fix (#597)

* refactored update fn to give the proper op with correct dates resolves #593

* removed uneeded code notes

lib/readers/elasticsearch_date_range/slicer.js

@@ -144,23 +144,17 @@ function newSlicer(context, opConfig, job, retryData, logger, client) {
     }
 
     function updateJob(opConfig, dates) {
-        var update = {};
-
-        if (!opConfig.start) {
-            update.start = dates.start;
-        }
-
-        if (!opConfig.end) {
-            update.end = dates.limit;
-        }
-
-        //this sends actual dates to execution context so that it can keep track of them for recoveries
-        if (update.hasOwnProperty('start') || update.hasOwnProperty('end')) {
+        // this sends actual dates to execution context so that it can keep
+        // track of them for recoveries
+        if (!opConfig.start || !opConfig.end) {
             var operations = JSON.parse(process.env.job).operations;
             operations.shift();
+            var update = {
+                start: dates.start.format(dateFormat),
+                end: dates.limit.format(dateFormat)
+            };
             var updatedOpConfig = Object.assign({}, opConfig, update);
-            updatedOpConfig.start = updatedOpConfig.start.format(dateFormat);
-            updatedOpConfig.end = updatedOpConfig.end.format(dateFormat);
+
             operations.unshift(updatedOpConfig);
             events.emit('slicer:job:update', {update: operations})
         }