In case of a 500 error, attempt a GET to determine if the URI might be incorrect

fix for https://github.com/doctrine/DoctrinePHPCRBundle/issues/154
oh, are you saying the check login triggers the handleError on the request? if that is the case i would just remove the check for getCheckLoginOnServer here, as in the error case we should always check if the server even exists to provide a more accurate message.

btw, what if jackrabbit is not running at all?