Coalesced redundant code

src/node/src/client.js

@@ -80,11 +80,7 @@ function _write(chunk, encoding, callback) {
   var batch = {};
   batch[grpc.opType.SEND_MESSAGE] = this.serialize(chunk);
   this.call.startBatch(batch, function(err, event) {
-    if (err) {
+    callback(err);
-      callback(err);
-      return;
-    }
-    callback();
   });
 }