Points with different number of columns from multiple shards return incorrect result

See https://groups.google.com/forum/#!topic/influxdb/LuD7DJN49f8 for more details. Copying the given example for illustration:

```json
{
  "columns":[
      "time",
      "sequence_number",
      "column1",
      "column2",
      "column4",
      "column3"
   ],
   "points":[
      [
         1396374564460,
         1000001,
         "val_column1",
         "val_column2",
         "val_column4",
         "val_column3"
      ],
      [
         1395834696224,
         5190001,
         "val_column1",
         "val_column2",
         "val_column3" // <- this value is in column4's index
      ]
   ]
}
```