Unset the "has data changed" flag after loading stock items linked to a product.

[woutersamaey]

The flag is set incorrectly, because some product data was added to the stock item, making Magento believe there was an actual change, when in fact there wasn't. This is the best way to reset this.

[woutersamaey]

Keeping the "_hasDataChanges" clean leads to greater performance because no save will happen if there aren't any real changes. Not exactly the same, but there's also some discussion in #1306

[kiatng]

May be a better fix on skipping model save is to add this method:

// In app\code\core\Mage\CatalogInventory\Model\Stock\Item.php
    /**
     * Checks that stock item model has data changes.
     * Call save stock item if model need to save in DB
     *
     * @return boolean
     */
    protected function _hasModelChanged()
    {
        if (!$this->hasDataChanges()) {
            return false;
        }

        return $this->_getResource()->hasDataChanged($this);
    }

[colinmollenhour]

@woutersamaey Sorry, I should have looked at this long ago.. I approve of this change but while I was applying some other changes for #1306 I went ahead and implemented an alternative solution that is perhaps a bit more "kosher" in #2066. (adds a proper protected property to reference the stockItem instead of using _data).

[colinmollenhour]

Approve, but if #2066 is merged this does not need to also be merged.

[fballiano]

I think #2066 would be a more comprensive solution :-)

[fballiano]

Since #2066 is already merged we don't need this one.