fix(grid-store): move into callback scope

Author: Jessica Lord

lib/gridfs/grid_store.js

@@ -454,10 +454,11 @@ var writeFile = function(self, file, callback) {
               if (offset >= stats.size) {
                 fs.close(file, function(err) {
                   if (err) return callback(err);
-                });
-                self.close(function(err) {
-                  if (err) return callback(err, self);
-                  return callback(null, self);
+
+                  self.close(function(err) {
+                    if (err) return callback(err, self);
+                    return callback(null, self);
+                  });
                 });
               } else {
                 return process.nextTick(writeChunk);